Shift control apparatus and method for hybrid transmission applicable to hybrid vehicle

ABSTRACT

In shift control apparatus and method for a hybrid transmission suitable for use in a hybrid vehicle, at least one of a target drive torque and a target input revolution acceleration to be a value within a realizable region to be set as a drive torque command value or an input revolution command acceleration is corrected in such a manner that polarities of the target drive torque and the target input revolution acceleration are left unchanged, in a case where a combination of the target drive torque with the target input revolution acceleration falls out of a realizable region on two-dimensional coordinates of the drive torque and the input revolution acceleration, the drive torque command value and the input revolution acceleration command value contributing to controls of the main power source and the motor/generators in place of the target drive torque and the target input revolution acceleration.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to shift control apparatus and method fora hybrid transmission suitable for use in a hybrid vehicle in which amain power source such as an engine and motor/generators are mounted.The present invention particularly relates to the shift controlapparatus and method which are capable of having a differentialequipment (unit) interposed between the main power source and themotor/generators carry out a continuously variable shift operation.

2. Description of the Related Art

Such a kind of hybrid transmission as described above, for example,includes a differential unit having two degrees of freedom and which isconstituted by a planetary gear group or so forth. An input from theengine which is the main power source, an output to a drive system, anda plurality of motor/generators are mutually coupled to respectiverevolutional members of the differential unit so that powers from themotor/generators permit the continuously variable shift operation. Inthe above-described hybrid transmission, the motor/generators are drivenby means of an electric power of a battery. However, when this drivingis carried out, it is necessary for the motor/generators to be driven ata power equal to or lower than a power rating of the battery in the samecase as the drive for a normally available electrical equipment.

A Japanese Patent Application First Publication No. Heisei 9-191506published on Jul. 22, 1997 exemplifies a previously proposed techniquecontrolling the drive torque to the motor/generators (function asmotors) in accordance with a state of the battery. In the previouslyproposed technique disclosed in the above-identified Japanese PatentApplication First Publication, an electric vehicle in which a motor isdriven along with a charge-and-discharge of the battery which serves asa power source is prerequisite. When a state variable of the battery isvaried by a reference value or more such as reductions in a batteryvoltage or a battery residual capacity equal to or lower than areference value, a response speed of a torque control for a drive torquecommand to the motor is slowed so that an earlier deterioration of thebattery is prevented.

SUMMARY OF THE INVENTION

However, if the above-described technique is used to the hybridtransmission of the above-described type which is the prerequisite,viz., the hybrid transmission in which the input from the engine (mainpower source), the output to the drive system, and the motor/generatorsare mutually coupled via the differential unit having the two degrees offreedom and the powers from the motor/generators can modify limitlesslya ratio between input and output revolutions of the transmission (shiftratio) by means of the powers from the motor/generators, the batteryresidual capacity or battery voltage is lowered to a value equal to orlower than the reference value or a battery temperature is raised by avalue equal to or higher than a reference value. At this time, if acontrol form is adopted in which the response speed is slowed to thecommand of the motor/generator, the following problems occur.

In details, in such a kind of the hybrid transmission as describedabove, the drive torque to the output of the drive system and a shiftspeed (input revolution acceleration) are mutually related to eachother. As described in the previously proposed technique, if the drivetorques of the motor/generators in accordance with only the state of thebattery without the shift speed (input revolution acceleration) takeninto consideration are limited, there is a possibility that the shiftspeed (input revolution acceleration) is in an opposite direction to adirection that the driver has expected. If the shift speed (inputrevolution acceleration) is in the opposite direction that the driverhas desired, an input revolution speed variation (engine revolutionspeed variation) which is opposite to that the driver has expected froma driving operation occurs. There is a possibility of the shift suchthat a sense of incompatibility is given to the driver. Then, there isan anxiety that a reduction of a shift quality is introduced.

It is, therefore, an object of the present invention to provide shiftcontrol apparatus and method for a hybrid transmission of a hybridvehicle in which corrections for the drive torque command value andinput revolution acceleration command value are made in such a mannerthat a combination of a target drive (or driving) torque and a targetinput revolution acceleration fall within a realizable region, the drivetorque command value and input revolution acceleration command valuecontribute to controls over the main power source (engine) andmotor/generators so that a deterioration of the battery developed whenthe combination of the target drive (driving) torque and the targetinput revolution acceleration which fall out of the realizable regioncontributes to the control over the main power source (engine) and themotor/generators is prevented from occurring, and which are capable oferadicating the anxiety on the reduction in the shift quality by makingthis correction in such a way that the shift speed (input revolutionacceleration) is not in the opposite direction to that in which thedriver has expected to be directed

According to one aspect of the present invention, there is provided ashift control apparatus for a hybrid transmission, comprising: aplurality of revolutional members which are enabled to be arranged on apredetermined lever diagram; a differential unit having two degrees offreedom such that if revolution states of two revolutional membersthereof are determined, the revolutional states of the otherrevolutional members are determined, an input of a main power source(ENG), an output to a drive system, and a plurality of motor/generators(MG1, MG2) are coupled to the respective revolutional members of thedifferential unit to adjust a power from the motor/generators in such amanner that a shift ratio between the main power source and the drivesystem is varied continuously; a target drive torque calculating sectionthat calculates a target drive torque (T*_(oO)) to the drive system inaccordance with a driving condition; a target input revolution speedcalculating section that calculates a target input revolution speed(ω*_(E)) of one of the revolutional members which is coupled to the mainpower source (ENG); a target input revolution acceleration calculatingsection that calculates a target input revolution acceleration (u_(io))to converge an actual input revolution (ωi) into the target inputrevolution speed (ω*i); and a target value correcting section thatcorrects at least one of the target drive torque (T*_(oO)) and thetarget input revolution (u_(io)) to be a value within a realizableregion to be set as a drive torque command value (T*o) and an inputrevolution acceleration command value (u_(io)) in such a manner thatpolarities of the target drive torque (T*_(oO)) and the target inputrevolution acceleration (u_(io)) are left unchanged, in a case where acombination of the target drive torque with the target input revolutionacceleration falls out of a realizable region on two-dimensionalcoordinates of the drive torque and the input revolution accelerationrelated to a combination of the drive torque and the input revolutionacceleration which is feasible in a state of the presentmotor/generators, a battery for the motor/generators (MG1, MG2), and themain power source, the drive torque command value (T*o) and the inputrevolution acceleration command value (u_(io)) contributing to controlsof the main power source and the motor/generators (3) in place of thetarget drive torque (T*_(oO)) and the target input revolutionacceleration (u_(io)).

According to another aspect of the present invention, there is provideda shift control method for a hybrid transmission, the hybridtransmission comprising: a plurality of revolutional members which areenabled to be arranged on a predetermined lever diagram; and adifferential unit having two degrees of freedom such that if revolutionstates of two revolutional members thereof are determined, therevolutional states of the other revolutional members are determined, aninput of a main power source, an output to a drive system, and aplurality of motor/generators (MG1, MG2) are coupled to the respectiverevolutional members of the differential unit to adjust a power from themotor/generators in such a manner that a shift ratio between the mainpower source and the drive system is varied continuously, and the shiftcontrol method comprising: calculating a target drive torque (T*o) tothe drive system in accordance with a driving condition; calculating atarget input revolution speed (ω*_(E)) of one of the revolutionalmembers which is coupled to the main power source (ENG); calculating atarget input revolution acceleration (u_(io)) to converge an actualinput revolution (ωi) into the target input revolution speed (ω*i); andcorrecting at least one of the target drive torque (T*_(oO)) and thetarget input revolution acceleration (u_(io)) to be a value within arealizable region to be set as a drive torque command value (T*o) or aninput revolution acceleration command value (u_(io)) in such a mannerthat polarities of the target drive torque (T*o) and the target inputrevolution acceleration (u_(io)) are left unchanged, in a case where acombination of the target drive torque (T*o) with the target inputrevolution acceleration (u_(io)) falls out of a realizable region ontwo-dimensional coordinates of the drive torque (To) and the inputrevolution acceleration {(d/dt)ωi} related to a combination of the drivetorque and the input revolution acceleration which is feasible in astate of the present motor/generators, a battery (P_(B)) for themotor/generators (MG1, MG2), and the main power source, the drive torquecommand value (T*o) and the input revolution acceleration command value(u_(i)) contributing to controls of the main power source (ENG) and themotor/generators (MG1, MG2) in place of the target drive torque(T*_(oO)) and the target input revolution acceleration (u_(io)).

This summary of the invention does not necessarily describe allnecessary features so that the invention may also be a sub-combinationof these described features.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an example of a diagrammatically illustrated hybridtransmission to which the present invention of a shift control apparatusin a first preferred embodiment is applicable.

FIG. 1B is a lever diagram of the hybrid transmission shown in FIG. 1A.

FIG. 2 is a block diagram of a control system of the hydraulictransmission shown in FIG. 1A.

FIG. 3 is a schematic functional block diagram of a hybrid controller inthe control system shown in FIG. 2.

FIG. 4 is a diagrammatical view representing a variable characteristicof the drive torque requested from the vehicle.

FIG. 5 is a characteristic graph representing an engine speed to developan engine power with an optimum fuel economy.

FIG. 6 is a diagrammatical view representing a realizable regionillustrating a combination of a drive torque and an engine (input)revolution acceleration by a combination of which is feasible by abattery rated power of the hybrid transmission.

FIGS. 7A, 7B, and 7C are diagrammatical views of a relationship betweenthe feasible region which is the same as that in the case of FIG. 6 andan operating point position during a non-shaft operation, of arelationship between the feasible region and the operating pointposition in which a movement state of the operating point during theshift operation is a case wherein the operating point is still withinthe feasible region, and of a relationship between the feasible regionand the operating point position in which the movement state of theoperating point during the shift operation is out of the realizableregion.

FIG. 8 is an operational flowchart representing a control programrelated to a correction procedure of a target drive (or driving) torqueand a target engine (input) revolution acceleration executed by a targetvalue correcting section shown in FIG. 3.

FIG. 9 is an operational flowchart representing a control programrelated to a correction procedure of a target motor/generator torqueexecuted by a motor/generator torque command value correcting sectionshown in FIG. 3.

FIG. 10 is a regional diagrammatical view illustrating an operableregion of motor/generators.

FIG. 11 is a diagram representing a correcting practice of the targetmotor/generator torques executed by motor/generator torque command valuedetermining section shown in FIG. 3.

FIGS. 12A and 12B, representing a variation situation of a revolutionalenergy during the shift operation of the revolutional members in thehydraulic transmission and a diagram representing a relationship betweenthe revolition energy and the gear ratio and a variation rate withrespect to the gear shift ratio of the revolution energy.

FIGS. 13A, 13B, 13C, and 13D are explanatory views of correctionprocedures of the target drive (or driving) torque and target engine(input) revolution acceleration executed by the gear shift controlapparatus in the hybrid transmission in a second preferred embodiment ofthe shift control apparatus according to the present invention,diagrammatical view illustrating an operating point position during theno shift, diagrammatical view illustrating the movement state of theoperating point during the shift operation which is still within therealizable region, and a diagrammatical view when the operating point isout of the feasible region, and a diagrammatical view in a case wherethe movement state of the operating point of the shift is out of therealizable region to a degree that the operating point is out of thefeasible region to a degree which does not satisfy the shift speed lowerlimit value, respectively.

FIG. 14 is an operational flowchart representing a control programrelated to the correction procedure of the target drive (or driving)torque and target engine (input) revolution acceleration executed by theshift control apparatus shown in FIGS. 13A through 13D.

FIG. 15 is an operational flowchart representing a control programrelated to the correction procedure.

FIG. 16 is a diagrammatical view of a structure corresponding to FIG. 1Aof the hybrid transmission in a third preferred embodiment of the shiftcontrol apparatus according to the present invention.

FIG. 17 is a block diagram representing a control system of the hybridtransmission to which the shift control apparatus according to thepresent invention is applicable.

FIG. 18 is a diagrammatical view of regions shown on a two-dimensionalcoordinate of the engine (input) revolution acceleration and the drivetorque of a realizable region by means of motor/generators in the hybridtransmission shown in FIG. 16.

FIG. 19 is a diagrammatical view representing an overlapped part of arealizable region of FIG. 18 and a realizable region of FIG. 6.

FIGS. 20A, 20B, and 20C are integrally a diagrammatical view of how arealizable region by means of the motor/generators shown in FIG. 18 isvaried when a maximum torque of the motor/generators is varied as 20A,20B, and 20C.

FIG. 21 is an operational flowchart representing a control program on acorrection procedure of the target drive (or driving) torque and targetengine (input) revolution acceleration executed by the shift controlapparatus in a fourth preferred embodiment in the hybrid transmissionshown in FIG. 16.

FIG. 22 is a regional diagrammatical view representing the operableregion of the motor/generators in the hybrid transmission shown in FIG.16.

FIGS. 23A and 23B are characteristic diagrammatical views representing amaximum torque variation characteristics of first and secondmotor/generators MG1 and MG2 shown in FIG. 16, respectively.

FIG. 24 is an operational flowchart representing a correction processprogram of the target drive (Or driving) torque and target engine(output) revolution acceleration in a fifth preferred embodiment of theshift control apparatus according to the present invention.

FIG. 25 is an operational flowchart representing the correction processprogram of the target drive (driving) torque and target engine (input)revolution acceleration in a sixth preferred embodiment of the shiftcontrol apparatus according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will hereinafter be made to the drawings in order tofacilitate a better understanding of the present invention.

First Embodiment

FIG. 1A shows a hybrid transmission to which a shift control apparatusin a first preferred embodiment according to the present invention isapplicable. In the first embodiment, the hybrid transmission constitutesa transaxle for a front-engine-front-drive (so called, FF) car. In FIG.1A, a reference numeral 1 denotes a transmission casing in which aRavigneaux type planetary gear set 2 located at a left side in an axialdirection of transmission casing 1 (leftward direction and rightwarddirection as viewed from FIG. 1A) is incorporated and a compositecurrent two-layer motor 3 located at a right side in the axial directionof transmission casing 1 is incorporated. An engine (main power source)ENG is disposed at an outside (leftward direction) of the transmissioncasing 1. Ravigneaux type planetary gear set 2, engine ENG, andcomposite current two-layer motor 3 is coaxially disposed on a mainaxial line of the hybrid transmission. In transmission casing 1, acountershaft 6 and a differential gear unit 7 are juxtaposed to the mainaxial line with an offset and are also incorporated into transmissioncasing 1. Left and right driven road wheels 8 are drivingly coupled todifferential gear unit 7.

Ravigneaux type planetary gear set 2 is a combination of two singlepinion planetary gear groups 4 and 5 having a common pinion P2. One ofthe planetary gear groups located nearer to engine ENG is a first singlepinion planetary gear group 4 and the other of the planetary gear groupsis a second pinion planetary gear group 5. First single pinion planetarygear 4 is constituted by a sun gear S2 and a ring gear R2 to both ofwhich a long pinion P2 are meshed. A second single pinion planetary geargroup 5 is provided with a sun gear S1, a ring gear R1, and alarge-diameter short pinion P1 meshed to both of the sun gear S1 andring gear R1. The short pinion P1 is meshed with a common pinion P2. Inaddition, pinions P1 and P2 of the planetary gear groups 4 and 5 arerevolutionally supported by means of common carrier C.

Ravigneaux type planetary gear set 2 has a main elements of fourrevolutional members of sun gear S1, sun gear S2, ring gear R2, andcarrier C and is constituted by a differential unit 2 having the twodegrees of freedom such that if the revolution speeds of the tworevolutional members are determined, the revolution speeds of the othermembers are determined. An order of revolution speed of the fourrevolutional members is sun gear (fastest) S1, ring gear R2, carrier C,and sun gear S2 as shown by a lever diagram shown in FIG. 1B.

Composite current two-layer motor 3 is constituted by an inner rotor 3ri, an annular outer rotor 3 ro enclosing inner rotor 3 ri, both rotorsbeing revolutionally and coaxially supported within transmission casing1, a ring shaped stator 3 s coaxially mounted in an annular stator 3 sis fixedly mounted on transmission casing 1. Annular coil (stator) 3 sand inner rotor 3 ri constitutes a first motor/generator MG1 and annularcoil (stator) 3 s and outer rotor 3 ro constitutes a secondmotor/generator MG2. Each of motor/generators MG1 and MG2 functions as amotor which outputs individual direction and velocity (including a stop)in accordance with a supply current when the composite current issupplied as a load and functions as a generator developing an electricpower in accordance with a revolution by means of an external force. Asshown in the lever diagram of FIG. 1B, in the revolution speed orderfrom the four revolution speed members of Ravigneaux type planetary gearset 2, in the order of sun gear S1, ring gear R2, carrier C, and sungear S2, first motor/generator MG1, the input from engine ENG which isthe main power source, and the output to the road wheel drive system(Out), and second motor/generator MG2 are coupled.

If this connection is described in details in the following on the basisof FIG. 1A, ring gear R2 serves as an input element to which the enginerevolution is inputted as described above. A crankshaft of engine ENG iscoupled to ring gear R2. Sun gear S1 is coupled to first motor/generatorMG1 (rotor 4 ri) via a hollow axle 11 extended toward a rearwarddirection opposite to engine ENG. Sun gear S2 is coupled tomotor/generator MG2 (rotor 4 ro) via hollow axle 12 fitted to hollowaxle 11 and motor/generator MG1 with a clearance.

Carrier C serves as an output element on which the revolution isoutputted to the wheel drive system. An output gear 14 is coupled tocarrier C via a hollow connecting member (output axle) 12. Output axle14 is disposed between Ravigneaux type planetary gear set 2 andcomposite current two-layer motor 3 and revolutionally (rotatably)supported within transmission casing 1. Output gear 14 is meshed withcounter gear 15 on a countershaft 6. An output revolution oftransmission from output gear 14 is transmitted to differential gearunit 7 via counter gear 15 and via countershaft 6. Differential gearunit 7 distributes the output revolution from transmission into left andright driven wheels 8. These elements described above constitute a roadwheel drive system.

The hybrid transmission whose structure has been heretofore describedcan be represented by the lever diagram shown in FIG. 1B. A lateral axisof the lever diagram shown in FIG. 1B denotes a ratio of distancesbetween the respective revolution members determined according to a gearratio of the planetary gear of the planetary gear groups 4 and 5. Thatis to say, when the distance between ring gear R2 and carrier C is 1,the ratio of distance between sun gear S1 and ring gear R2 is denoted bya and the ratio of distance between carrier C and sun gear S2 is denotedby β. A longitudinal axis of the lever diagram denotes a revolutionspeed of each revolutional member. In details, an engine revolutionspeed ω_(E) to ring gear R2 (transmission input revolution speed(ω_(i)), a revolution speed ω₁ of) motor/generator) sun gear S1,revolution speed ωo of the transmission output (Out) from carrier C, andrevolution speed ω₂ of sun gear S2 (motor/generator MG2). If therevolution speeds of the two revolutional members are determined, theother two revolutional members are determined.

A shift operation of the hybrid transmission will hereinafter bedescribed with reference to the lever diagram shown in FIG. 1B. Theshift operation when a (vehicular) forward (positive) revolution isoutputted includes two modes of EV mode and EIVT mode and a backward(reverse) revolution is outputted includes a REV shift operation. In theEV mode, as shown in lever EV shown in FIG. 1B, the output (Out) to theroad wheel drive system is determined only by means of a power from bothof motor/generators MG1 and MG2 (or one of the motor/generators) withengine ENG stopped. In the EIVT mode, as illustrated in lever EIVT modeof FIG. 1B, the output (Out) to the road wheel drive system isdetermined by means of the powers from engine ENG and both of themotor/generators MG1 and MG2.

The REV shift operation for the backward (reverse) revolution output isnot dependent upon the power from engine ENG as shown by a lever REV inFIG. 1B but according to the positive revolution of the onemotor/generator MG1, or the reverse revolution of the othermotor/generator MG2, or both of the motor/generators (MG1, MG2)revolution from carrier C is outputted to output (Out).

A shift control system of hybrid transmission carrying out the shiftoperation control in each mode described above is constituted as shownin FIG. 2. A hybrid controller 21 performs an integration control ofboth engine ENG and the hybrid transmission. Hybrid controller 21supplies commands on target torque T*_(E) and on target revolution speed(ω*_(E)) (target input revolution speed ω*₁) of engine ENG to an enginecontroller 22. Engine controller 22 drives engine ENG to have engine ENGachieve this target values T*_(E) and ω*_(E) (ω*_(i)). Hybrid controller21, furthermore, supplies command signals on target torques T*₁ and T*₂of motor/generators MG1 and MG2 to motor controller 23. Motor controller23 controls motor/generators MG1 and MG2 by means of an inverter 24 anda battery 25 to achieve target torques T*₁ and T*₂. Hybrid controller 21inputs a signal from an accelerator opening angle sensor 26 to detect anaccelerator opening angle APO from an accelerator pedal depressiondepth, a signal from a vehicle speed sensor 27 to detect a vehicle speedVSP (which is proportional to output revolution speed (=ωo), and asignal from an engine speed sensor 28 to detect the engine speed ω_(E)(=input revolution speed, ω_(i)).

Hybrid controller 21 carries out a mode selection to achieve the drivingstate that the driver has desired from the accelerator pedal depressiondepth (accelerator opening angle) APO and vehicle speed VSP, and acharged state of battery 25 (SOC state of charge (carrying out enablingpower) and executes the shift control in accordance with the selectionmode to determine and command the target engine torque T*_(E), targetengine speed ω*_(E) (ω*i), and target motor/generator torques T*₁ andT*₂.

It is noted that revolution speed information inputted to hybridcontroller 21 is not limited to engine speed ω_(E) (ωi) and vehiclespeed VSP (vehicle speed and output revolution speed ωo). Since thedifferential unit constituted by Ravigneaux type planetary gear set 2has two degrees of freedom, the revolution speeds of any two of therevoltutional members may be inputted to hybrid controller 21.

FIG. 3 shows a functional block diagram of hybrid controller 21. Hybridcontroller 21 includes an input revolution servo controlling section102, a target value correcting section 103, a motor/generator torquedistributing section 104, a motor/generator torque command valuedetermining section 105, and a target engine torque correcting section106. Target value generating section 101 calculates a target drivingtorque T*_(oO) to the road wheel drive system, a target enginerevolution speed ω*_(E), and a target engine torque T*_(E)o from anaccelerator pedal depression depth (opening angle) APO, the vehiclespeed VSP, and a battery charge state SOC (bringing out enabling power).

Hence, at first, target driving torque T*_(oO) to transmission outputgear 14 is calculated using a drive torque map shown in FIG. 4 fromaccelerator depression depth (opening angle of the accelerator APO),vehicle speed VSP. Vehicle speed VSP is calculated using the followingequation (1) from, for example, output axle revolution speed ωo.VSP=k _(v) ·ωo  (1),wherein kv denotes a constant determined according to a radius of a tireand a final gear ratio. Next, target value generating section 101calculates a target driving power P*o from target driving torque T*o andoutput revolution speed ωo as follows:P*o=ωo×T*o  (2).Next, target value generating section 101 determines a target batterycharge-and-discharge quantity P*_(B) in such a manner that, as SOCbecomes high, the battery discharge quantity becomes increased and, asSOC becomes low, the battery charge quantity becomes increased.

Finally, target engine revolution speed ω*i and target engine torqueT*_(EO) are calculated as follows from target driving power P*o, enginespeed ωi, and target battery charge-and-discharge quantity P*_(B). Thetarget engine power P*_(E) is set in such a way that target engine powerP*_(E), target driving power P*o, and target charge-and-dischargequantity P*_(B) have the relations expressed by the following equation:P* _(E) =P*o+P* _(B)  (3).Next, target engine (revolution) speed ω*E at which the fuel consumptionbecomes optimum when the target engine power P*_(E) is generated by theengine is searched from target engine power P*_(E) using a fuelconsumption optimum target engine speed map shown in FIG. 5.

In order to supply target engine power P*E with the engine and to makean engine operating point a fuel consumption optimum point, there is athought that a value of target engine power P*_(E) divided by targetengine revolution speed ω*_(E) should be target engine torque T*_(E).However, target value correcting section 103 as will be described lateroften limits the 4engine (input) revolution acceleration during a shifttransient state. In this case, target engine revolution speed ω*E is notbe realized. As described above, in a case wherein target enginerevolution speed ω*_(E) is not realized, target engine power P*_(E)cannot be obtained. Therefore, target engine torque T*_(EO) is a valueof target engine power P*_(E) divided by an actual engine (revolution)speed ω_(I), as expressed by the following equation.

$\begin{matrix}{T_{EO}^{*} = {\frac{P_{E}^{*}}{\omega_{i}}.}} & (4)\end{matrix}$

It is noted that if target engine revolution speed ω*_(E) is coincidentwith actual engine (revolution) speed WE during a steady state, theengine torque gives an engine torque whose fuel consumption is optimum.Referring to FIG. 3, an input revolution servo controlling section 102inputs a deviation between target engine revolution speed ω*_(E) andactual engine revolution speed ω_(E) and calculates a target engine(input) revolution acceleration u_(io) so that the deviation of theinput revolution (engine revolution) is decreased. When this calculationis carried out, target engine (input) revolution acceleration u_(io) maybe calculated, for example, using a sliding mode controller as shown inthe following equation.

$\begin{matrix}{u_{io} = {K\;{\frac{\sigma}{{\sigma } + ɛ}.}}} & (5)\end{matrix}$σ=ω*_(E)−ωi  (6),

wherein ε denotes a constant determining an upper limit of target engine(input) revolution acceleration u_(io) and denotes a positive constantwhich makes target engine (input) revolution acceleration u_(io)continuous in a proximity to zero of σ.

Referring to FIG. 3, target value correcting section 103 serves tocorrect target drive torque (or target driving torque) T*_(oO) andtarget engine (input) revolution acceleration u_(io) to a value withinthe realizable region in a case where a combination of the drive torqueTo and engine (input) revolution acceleration dωi/dt (or expressed as{(d/dt)ωi} which can be realized under the present engine and state ofthe battery is expressed on two-dimensional coordinates shown in FIG. 6with the drive torque To as a lateral axis and with an engine (input)revolution acceleration dω_(i)/dt as a longitudinal axis and the targetdrive (driving) torque T*_(oO) and target engine (input) revolutionacceleration dΩ_(i)/dt falls out of the realizable region expressed ontwo-dimensional coordinates shown in FIG. 6.

A relationship from among drive torque To, engine (input) revolutionacceleration dω_(i)/dt, engine revolution speed ωi, output revolutionspeed ωo, running resistance torque T_(R), engine torque T_(E), andbattery charge-and-discharge quantity P_(B) is expressed in thefollowing equation (7).

$\begin{matrix}{{{( {{k_{ii}\omega_{i}} + {k_{io}\omega_{o}}} )\frac{d\;\omega_{i}}{ct}} + {( {{k_{oi}\omega_{i}} + {k_{00}\omega_{o}}} )T_{o}}} = {{k_{R}T_{R}} + {k_{E}T_{E}} + {P_{B}.}}} & (7)\end{matrix}$

It is noted that k_(ii), k_(io), k_(oi), k_(oo), k_(R), and k_(E) denoteconstants determined according to the specifications (inertia moment andradius of revolutional elements in the planetary gear unit of the hybridsystem). In this equation (7), it is possible to detect the presentengine speed ω_(i) and output revolution speed ωo are detectable andrunning resistance torque T_(R) and engine torque T_(E) can be estimatedusing, for example, an external disturbance observer. As shown in FIG.6, with lateral axis as the drive torque To and longitudinal as engine(input) revolution acceleration dωi, the two-dimensional coordinates isformed. From the range of battery charge-and-discharge quantity usingthe above equation (7), a region in which drive torque To and engine(input) revolution acceleration dωi/dt fall in a battery rated power (arealizable region) is obtained as shown in A of FIG. 6.

In this two-dimensional coordinate, suppose that a target operatingpoint determined according to target drive (or driving) torque T*_(oO)and target engine (input) revolution acceleration u_(io). If this targetoperating point falls out of the realizable region, target operatingpoint does not fall within the battery rated power so that a life of thebattery becomes short. Hence, as described below, signs of these targetdrive (driving) torque T*_(oO) and target engine (input) revolutionacceleration u_(io) is corrected within the value of the realizableregion to define a drive torque command value T*o and target engine(input) revolution acceleration u_(i). A method of correcting targetdrive (driving) torque T*_(oO) and target revolution acceleration u_(io)will be described below with reference to FIGS. 7A, 7B, and 7C.

In FIGS. 7A, 7B, and 7C, a target operating point expressed by thecombination of target drive (driving) torque T*_(oO) and target engine(input) revolution acceleration u_(io) before the correction is denotedby o (circle in white) and a command operating point expressed as acombination of a drive torque command value T*o and target engine(input) revolution acceleration u_(i) after the correction of thesephysical values is made is denoted by • (circle in black).

Target operating point ? shown in FIG. 7A indicates a running state at acertain target drive (driving) torque T*_(oO) without shift (engine(input) revolution acceleration dωi/dt=0). After this, when acceleratorpedal is depressed, target operating point ? of FIG. 7A is moved to abroken line denoted by FIG. 7B. In FIG. 7B, since target operating pointis present within the realizable region A, the corrections for targetdrive (driving) torque T*oD and target engine (input) revolutionacceleration u_(io) is not carried out.

Thereafter, when target operating point o is moved furthermore asdenoted by a broken line in FIG. 7C, target operating point o becomesout of realizable region A and the combination of target drive (driving)torque T*_(oO) and target engine acceleration u_(io) cannot be realizedwhich is fastest responded cannot be achieved but also becomes out ofthe battery rated power so that the life of the battery becomesintroduced. In this case, target value correcting section 103, in thetwo-dimensional coordinates of drive torque To and engine (input)revolution acceleration dωi/dt shown in FIG. 7C, assumes the point ofcircle black • nearest to the target operating point o which is on aline segment denoted by a solid line connecting between the origin onthe two-dimensional coordinate and target operating point ocorresponding to the combination of target drive (driving) torqueT*_(oO) and target engine (input) revolution acceleration u_(io). Then,target value correcting section corrects target drive (driving) torqueT*_(oO) and target engine acceleration u_(io) at the target operatingpoint ? to drive torque T*o and engine (input) revolution accelerationu_(i) at command operating point • and these corrected drive torque T*oand engine (input) revolution acceleration u_(i) is set as the drivetorque command value and engine acceleration command value and commandedto motor/generator torque distributing section 104.

Target value correcting section 103 executes the correction process oftarget drive (driving) torque T*_(oO) and target engine (input)revolution acceleration u_(io) (determination of drive torque commandvalue T*o and engine (input) revolution acceleration command valueu_(i)) in accordance with a flowchart shown in FIG. 8.

At a step S10, target value correcting section 103 derives realizableregion A expressed on the two-dimensional coordinate of drive torque Toand engine (input) revolution acceleration (d/dt)ωi shown in FIGS. 6 and7 and two boundary lines prescribing this region. These two boundarylines can be calculated in the following equation in which P_(B) inequation (7) is replaced with a battery rated power±P_(Bmax).

$\begin{matrix}{{{( {{k_{ii}\omega_{i}} + {k_{io}\omega_{o}}} )\frac{\mathbb{d}\omega_{i}}{\mathbb{d}t}} + {( {{k_{oi}\omega_{i}} + {k_{oo}\omega_{o}}} )T_{0}}} = {{k_{R}T_{R}} + {k_{E}T_{E}} + {P_{B\mspace{11mu}\max}.}}} & (8) \\{{{( {{k_{ii}\omega_{i}} + {k_{io}\omega_{o}}} )\frac{\mathbb{d}\omega_{i}}{\mathbb{d}t}} + {( {{k_{oi}\omega_{i}} + {k_{oo}\omega_{o}}} )T_{o}}} = {{k_{R}T_{R}} + {k_{E}T_{E}} - {P_{B\mspace{11mu}\max}.}}} & (9)\end{matrix}$

At step S11, target value correcting section 103 derives points ofintersections (x₁, y₁) and (x₂, y₂) of a straight line denoted by a boldsolid line shown in FIG. 7C, passing through target operating point owhich is the combination of target drive (driving) torque x₀ (=T*_(oO))and target engine (input) revolution acceleration y₀ (=u_(io)) expressedin the equation (9) and an origin 0 of the two-dimensional coordinatesand boundary lines calculated from the above equations (8) and (9)(wherein x₁<x₂ and x₁ and x₂ denote drive torques and y₁ and y₂ denoteengine (input) revolution accelerations).

$\begin{matrix}{\frac{\mathbb{d}\omega_{i}}{\mathbb{d}t} = {\frac{u_{io}}{T_{oO}^{*}}{T_{o}.}}} & (10)\end{matrix}$

At a step S12, target value correcting section 103 determines whether x₀falls between x₁ and x₂. If x₀ is determined to be within x₁ and x₂(yes), the routine goes to a step S13 since target drive (driving)torque T*o and target engine (input) revolution acceleration u_(io)falls within a realizable region A. If x₀ is determined not to fallwithin x₁ and x₂ (no), the control goes to a step S14 since target drive(driving) torque and target engine (input) revolution acceleration isout of realizable region A.

At step S13 selected when the above-described target drive (driving)torque and target engine (input) revolution acceleration fall within therealizable region A, target operating point o which is the combinationof target drive (driving) torque x₀ (=T*_(oD)) and target engine (input)revolution acceleration y₀(=U_(io)) is directly set as thepost-correction drive torque command value T_(o)* and target driveengine (input) revolution acceleration u_(io) is directly set as thepost-correction engine (input) revolution acceleration u_(i). At stepS14 selected when the above-described target drive (driving) torque andtarget engine (input) revolution acceleration do not fall withinrealizable region A. The operating points of one of both of (x₁. y₁) and(x₂, y₂) which is nearer to (x₀, y₀) is served as the command operatingpoint and the drive torque T*_(o) and engine (input) revolutionacceleration u_(i) are respectively set as the post-correction drivetorque command value T*_(o) and the post-correction engine (input)revolution acceleration command value u_(i). Hence, post-correctiondrive torque command value T*o and post-correction engine (input)revolution acceleration value u_(i) have the same sign (polarity) astarget drive (driving) torque T*_(oO) and target engine (input)revolution acceleration u_(io).

Referring back to FIG. 3, motor/generator torque distributing section104 determines target torques (target motor/generator torques) T*₁₀ andT*₂₀ of motor/generators MG1 and MG2 to achieve post-correction drivetorque command value T*o and post-correction engine (input) revolutionacceleration command values u_(i) (transmission command value) even inthe steady state nor in the transient state. To determine this targettorques T*₁₀ and T*₂₀, the following relationship is established fromamong engine (input) revolution acceleration dω_(i)/dt, runningresistance torque T_(R), engine torque T_(E), and the relationshipbetween torques T_(1 and T) ₂ of motor/generators MG1 and MG2.

$\begin{matrix}{\frac{\mathbb{d}\omega_{i}}{\mathbb{d}t} = {{b_{11}T_{R}} + {b_{12}T_{E}} + {b_{13}T_{1}} + {b_{14}{T_{2}.}}}} & (11)\end{matrix}$

In addition, the following relationship is established from among drivetorque To, running resistance torque T_(R), engine torque T_(E), andmotor/generator torques T₁ and T₂ are established.T ₀ =b ₂₁ T _(R) +B ₂₂ T _(E) +b ₂₃ T ₁ +b ₂₄ T ₂  (12).When equation (11) and equation (12) are combined, the followingequation is established.

$\begin{matrix}{{\begin{bmatrix}T_{1} \\T_{2}\end{bmatrix} = {{{A_{c}^{- 1}( {\begin{bmatrix}\frac{\mathbb{d}\omega_{i}}{\mathbb{d}t} \\T_{0}\end{bmatrix} - {B_{c}\begin{bmatrix}T_{R} \\T_{E}\end{bmatrix}}} )}.A_{C}} = \begin{bmatrix}b_{13} & b_{14} \\b_{23} & b_{24}\end{bmatrix}}},{B_{c} = \begin{bmatrix}b_{11} & b_{12} \\b_{21} & b_{22}\end{bmatrix}}} & (13)\end{matrix}$

If, in equation (13), drive torque To is replaced with post-solutiondrive torque command value T*o, target engine (input) revolutionacceleration (d/dt)ωi is replaced with post-correction engine revolutioncommand value u_(i), furthermore, torques T₁ and T₂ of motor/generatorsMG1 and MG2 are replaced with target motor/generator torques T*₁₀ andT*₂₀, the following equation is obtained, the following equations areobtained. From this equation, target motor/generator torques T*₁₀ andT*₂₀ can be obtained.

$\begin{matrix}{\begin{bmatrix}T_{10}^{*} \\T_{20}^{*}\end{bmatrix} = {{A_{c}^{- 1}( {\begin{bmatrix}u_{i} \\T_{0}^{*}\end{bmatrix} - {B_{c}\begin{bmatrix}T_{R} \\T_{E}\end{bmatrix}}} )}.}} & (14)\end{matrix}$

It is noted that, running resistance torque T_(R) and engine torqueT_(E) may directly be detected or, alternatively, may be estimated usingan external disturbance observer. In either case, these runningresistance torque T_(R) and engine torque T_(E) may easily bedetermined.

A motor/generator torque command value determining block 105 in FIG. 3determines motor/generator torque command values T*₁ and T*₂ bycorrecting target motor/generator torques T*₁₀ and T*₂₀ to values withinthe torque range in which target motor/generator torques T*₁₀, T*₂₀ canbe outputted in a case where each target motor/generator torques T*₁₀and T*₂₀ obtained by motor/generator torque distributing section 104 asdescribed above is in excess of a mechanically output enabled torquerange and in a case where the achieved target motor/generator torqueT*₁₀ and T*₂₀ is in excess of the battery rated power.

Thus, motor/generator torque command value determining section 105limits motor/generator torques T*₁₀ and T*₂₀ within an output enabledtorque range and limits the same target motor/generator torques tobecome excessive with respect to the battery rated power. Theselimitations serve to function to protect a earlier deterioration ofmotor/generators MG1 and MG2 and to protect a demand exceeding thebattery rated power from deteriorating the battery at an early timing.

One example of an algorithm executed by motor/generator torque commandvalue determining section 105 in which target motor/generator torquesT*₁₀, T*₂₀ are corrected to values within the output enabled operatingenabling (operable) range to determine motor/generator torque commandvalue T*₁ and T*₂ will be described in details with reference to anoperational flowchart shown in FIG. 9.

At a step S20, motor/generator torque command value determining section105 determines whether each of target motor/generator toques T*₁₀ andT*₂₀ is within the mechanically output enabled torque range and iswithin the operable region not exceeding the battery rated power.

The operable region of target motor/generator torques T*₁₀ and T*₂₀ willbe described with reference to two-dimensional coordinates of FIG. 10,with torque T₁ of first motor/generator taken along a lateral axis ofFIG. 10 and torque T₂ of second motor/generator MG2 taken along alongitudinal axis of FIG. 10.

In details, the following relationship is established from among batterycharge-and-discharge quantity P_(B), revolution speed ω₁ and torque T₁of first motor/generator MG₁, and revolution speed ω₂ and torque T₂ ofsecond motor/generator MG₂.P_(B)=ω₁T₁+ω₂T₂  (15).

It is noted that the present engine (revolution) speed ω₁ and outputrevolution speed ω_(o) are detectable. Using equation (15), a region FAwhich is a region in which the drive torque and engine revolution speedfall within the battery rated power from the range of batterycharge-and-discharge quantity P_(B) is obtained as shown in FIG. 10.Next, a mechanical operation range of composite current two-layer motor3 can be determined as a region FB shown in FIG. 10 as appreciated fromthe following explanation. That is to say, in the case of compositecurrent two-layer motor 3, the following relationship is present betweenrevolution speeds x₁ and ω₂ of the first and second motor/generators MG1and MG2 and mechanical torque maximum values T_(1max) and T_(2max).Torque maximum value T_(1max) of first motor/generator MG1 is expressedby a non-linear function f, of torque maximum value T_(2max) of secondmotor/generator MG2 and of revolution speeds ω₁ and ω₂ of bothmotor/generators MG1 and MG2.T _(1max) =f ₁(T _(2max), ω₁, ω₂)  (16).Using equation (16), from the present revolution speeds ω₁ and ω₂ offirst and second motor/generators MG1 and MG2, a relationship betweenmechanical torque maximum values T_(1max) and T_(2max) of first andsecond motor/generators MG1 and MG2 is obtained. From this relationship,a mechanical operation range of composite current two-layer motor 3 canbe obtained as denoted by region FB of FIG. 10.

Furthermore, in order to prevent engine (input) revolution acceleration(shift speed) from being placed in the proximity to zero by apredetermined value y_(min) when target motor/generator torques T*₁₀ andT*₂₀ are corrected, a torque range of first and second motor/generatorsMG1 and MG2 at a time when engine (input) revolution accelerationindicates a value toward the engine revolution speed acceleration sidethan the predetermined value y_(min) at a time when the ante-correctiontarget motor/generator torques T*₁₀ and T*₂₀ are achieved is determinedas a region FC in FIG. 10. This region FC is set using equation (11) soas to satisfy the following conditions.If b ₁₁ T _(R) +b ₁₂ T _(E) +b ₁₃ T* ₁₀ +b ₁₄ T* ₂₀≦0, b ₁₁ T _(R) +b ₁₂T _(E) +b ₁₃ T ₁ +b ₁₄ T ₂ ≦y _(min)  (17).If b ₁₁ T _(R) +b ₁₂ T _(E) +b ₁₃ T* ₁₀ +b ₁₄ T ₂≦0, b ₁₁ T _(R) +b₁₂T_(E) +b ₁₃ T ₁ +b ₁₄ T ₂ ≦y _(min)  (18).It is noted that the above-described predetermined value y_(min) may beset as follows:

$\begin{matrix}{{y_{\min} = {{ky}\;\frac{\sigma_{y}}{\lbrack \sigma_{y} \rbrack + ɛ_{y}}}},} & (19)\end{matrix}$wherein σy: a deviation between target input revolution speed and actualinput revolution speed, εy: a positive constant to make continuousy_(min) when σy=0, and Ky denotes a positive constant obtained byexperiments or computer simulation.

A region FX on which the above-described region FA in thetwo-dimensional coordinate, region FB, and region FC are overlapped, onthe two-dimensional coordinates of both of motor/generator torques shownin FIG. 10 is the above-described operable region. In a case where threeconditions described below are satisfied, target motor/generator torquesT*₁₀, T*₂₀ fall in the operable region FX.

(Condition 1)

The battery charge-and-discharge quantity P_(B) obtained by substitutingtarget motor/generator torques T*₁₀ and T*₂₀ into equation (15) is equalto or below a battery rated power.

(Condition 2)

Target motor/generator torque T*₁₀ is smaller than torque maximum valueT_(imax) of first motor/generator MG1 obtained by substituting targetmotor/generator torques T*₂₀ into equation (16) and targetmotor/generator torque T*₂₀ is smaller than torque maximum valueT_(2max) of motor/generator torque MG2 obtained by substituting targetmotor/generator torque T*₁₀ into equation (16).(Condition 3)If b₁₁T_(R)+b₁₂T_(E)+b₁₃T*₁₀+b₁₄T*₂₀≧0, target motor/generator torquesT*₁₀ and T*₂₀ satisfy the relationship of equation (17) and, ifb₁₁T_(R)+b₁₂T_(E)+b₁₃T*₁₀+b₁₄T*₂₀≦0, target/motor generator torques T*₁₀and T*₂₀ satisfy the equation (18).

At a step S20 in FIG. 9, motor/generator torque command valuedetermining section 105 determines whether the above-described threeconditions are satisfied and both of target motor/generator torques T*₁₀and T*₂₀ fall within operable region FX shown in FIG. 10.

If both of target motor/generator torques T*₁₀ and T*₂₀ fall within theoperable region FX at step S20, the routine goes to a step S21. At stepS21, motor/generator torque command value determining section 105directly sets target motor/generator torques T*₁₀ and T*₂₀ withoutcorrection as motor/generator torque command values T*₁ and T*₂. Iftarget motor/generator command values T*₁₀ and T*₂₀ are out of operableregion FX, at a step S22, motor/generator torque command valuedetermining section 105 corrects target motor/generator torques T*₁₀ andT*₂₀ to values within operable region FX in such a manner that avariation of the drive torque is minimized and sets the corrected targetmotor/generator torques T*₁₀ and T*₂₀ as motor/generator torque commandvalues T*₁ and T*₂.

The correction procedures carried out at steps S21 and S22 of FIG. 9 fortarget motor/generators T*₁₀ and T*₂₀ will hereinafter be described onthe basis of FIG. 11 in which operable region FX is extracted from FIG.10.

In FIG. 11, o denotes an ante-correction operating point which is acombination of target motor/generator torques T*₁₀ and T*₂₀ which arebefore the correction processing and • denotes a post-correctionoperating point which is a combination of motor/generator torque commandvalues of T*₁ and T*₂. A straight line passing through ante-correctionoperating point o indicates the combination of motor/generator torquesT_(1 and T) ₂ which develops the same drive torque as drive torque Towhich can be obtained from equation (12) achievable according to therealization of ante-correction target motor/generator torque commandvalues T*₁₀ and T*₂₀.

Patterns on the correction procedures of target motor/generator torquesT*₁₀ and T*₂₀ are three patterns of pattern A, pattern B, and pattern C.Individual patterns thereon will be described below.

<<Pattern A>>

This pattern is a case where the ante-correction operating point o(target motor/generator torques T*₁₀ and T*₂₀) is present in operableregion FX. In this case, as described above with reference to step S21of FIG. 9, target motor/generator torques T*₁₀ and T*₂₀ are notcorrected and these are set directly as the post-correctionmotor/generator torque command values T*₁ and T*₂.

<Pattern B>>

Pattern B is a case where ante-correction operating point o (targetmotor/generator torques T*₁₀ and T*₂₀) is out of operable region FX butan equi(equivalent)—drive torque straight line passing through theante-correction operating point o is intersected across operable regionFX. In this case, at step S22 of FIG. 9, operating point • nearest toante-correction operating point o and which is on the equi-drive torquestraight line passing through the ante-correction operating point o andfalls within the operable region FX is set as a post-correctionoperating point. The motor/generator torque command values T₁ and T₂ atthis post-correction operating point ? are post-correctionmotor/generator torque command values T*₁ and T*₂. In this case, thedrive torque is not changed even by the correction of targetmotor/generator torques T*₁₀ and T*₂₀ which (motor/generator torquecommand values T*₁ and T*₂).<Pattern C>>Pattern C is a case where ante-correction operating point o (targetmotor/generator torques T*₁₀, T*₂₀) falls out of operable region FX andthe equi-drive torque straight line is not intersected with the operableregion FX. In this case, the operating point which can generate the samedrive torque as the drive torque obtained by the achievement ofante-correction target motor/generator torques T*₁₀ and T*₂₀ is notpresent, Therefore, at step S22 of FIG. 9, the operating point ? whichis within the operable region FX and which is nearest to the equi-drivetorque straight line passing through ante-operating point o is set asthe post-correction operating point. The correction of targetmotor/generator torques T*₁₀ and T*₂₀ are corrected so thatmotor/generator torques T₁ and T₂ at this post-correction operatingpoint ? is set as the post-correction motor/generator torque commandvalues T*₁ and T*₂. In this case, the variation in the drive torquealong with the correction of target motor/generator torques T*₁₀ andT*₂₀ (motor/generator torque command values T*₁ and T*₂) can besuppressed at minimum.

According to the corrections of target motor/generator torques T*₁₀ andT*₂₀ described above, if the combination of target torques T*₁₀ and T*₂₀of both motor/generators MG1 and MG2 (ante-correction operating point oin FIG. 11), as described in pattern A and pattern C, is out of operableregion FX determined according to the rated-power of the battery and thecapabilities of motor/generators MG1 and MG2, this combination iscorrected to the value within operable region FX to provide acombination of motor/generator torque command values T*₁ and T*₂.(post-correction operating point • of FIG. 11). This combinationcontributes on the control over motor/generators. Therefore, drivecommands which exceed the capabilities of motor/generators MG1 and MG2themselves and the rated power of the battery are not received.Consequently, reductions of the life of the battery and of durability ofmotor/generators MG1 and MG2 can be avoided.

When the corrections of target motor/generators T*₁₀ and T*₂₀ arecarried out, the corrections are made so that the polarities of thedrive torque and engine (input) revolution acceleration according to thepost-correction motor/generator torque command values T*₁ and T*₂ arethe same as the drive torque and engine (input) revolution accelerationby means of ante-correction target motor/generator torques T*₁₀ andT*₂₀. The generation of the drive torque and the engine (input)revolution acceleration which are opposite to the desired drive torqueand the desired engine (input) revolution acceleration by means of theante-correction target motor/generator torques can be avoided. Anunnatural variation in the drive torque and shift speed can be preventedand unpleasant vehicular acceleration/deceleration and the problems onthe transmission quantity having the sense of incompatibility can beeliminated.

When the corrections of target motor/generator torques T*₁₀ and T*₂₀ aremade, motor/generator torque command values T*₁ and T*₂ are determinedto be the same value as the driving torque obtained by the drive torqueby means of ante-correction target motor/generator torques T*₁₀ and T*₂₀or the value within the region which is nearest to the drive torquedescribed above. Hence, even if the correction of target motor/generatortorques T*₁₀ and T*₂₀ is made, the variation in the drive torque ispresent or an unpleasant vehicular acceleration/deceleration feeling canbe eliminated with at least the variation in the drive torque minimized.

In addition, when target motor/generator torques T*₁₀ and T*₂₀ arecorrected, within a region of the two-dimensional coordinates ofT_(1 and T) ₂ in which the engine (input) revolution acceleration dωi/dt(shift speed) indicates a value toward which the ante-correctionrevolution acceleration side than predetermined value y_(min) between 0and ante-correction revolution acceleration obtained by theante-correction target motor/generator torques T*₁₀ and T*₂₀, thecorrection is carried out so that a difference between the drive torquesbefore and after the corrections of target motor/generator torques T*₁₀and T*₂₀ is minimized and the target motor/generator torques T*₁₀ andT*₂₀ are corrected to be set as motor/generator torque command valuesT*₁ and T*₂. Hence, the variation of the drive torque is minimized sothat an unpleasant vehicular acceleration or deceleration feeling can besuppressed with the shift speed faster than predetermined value y_(min)maintained even if target motor/generator torques T*₁₀ and T*₂₀ arecorrected.

Referring back to FIG. 3, target engine torque correcting section 106serves to correct target engine torque T*_(EO) in such a manner that apower needed to the gear shift is provided from the engine. Thefollowing relationship is present from among a power Pi required for therevolution speed variation of the revolutional members constituting thepower transmission mechanism, engine power P_(E), motor/generator powerP_(B), and drive power Po.P _(E) +P _(B) =P _(i) +P _(o)  (20).Hence, even when the revolution speed of any revolutional member in thehybrid transmission such as during the shift operation, it is necessaryto supply the power needed for the gear shift by means of engine ENG ormotor/generators MG1 and MG2 in order to achieve the target drive(driving) torque.

However, since motor/generator power P_(B) is equal to batterycharge-and-discharge quantity, a load on the battery is increased whenthe power required for the shift by means of motor/generators MG1 andMG2 and there is a possibility that the increase of the load exceeds thebattery rated power. Because motor/generators MG1 and MG2 compensatesfor the lack of engine power due to a lag with respect to the targetvalue of the engine torque. Therefore, the power required for the shiftis supplied from the engine. It is noted that, as in the case of thehybrid transmission in the first embodiment, the power from a pluralityof power sources using the differential unit constituted by theplanetary gear mechanism is outputted to the drive axle, a revolutionalsystem kinetic energy as conventional transmission is often notmonotonously varied according to the gear ratio depending upon aspecification of the hybrid transmission.

The relationship between the gear shift ratio i_(c) of the hybridtransmission and kinetic energy U is as shown in FIG. 12A. Therevolutional kinetic energy U takes a minimum value at a certainpredetermined gear ratio i_(co). Hence, in the conventionaltransmission, although the sign of the revolution kinetic energyvariation is the same provided that the direction of the shift isconstant, In the case of the hybrid transmission, even if the shiftdirection is constant, the direction of the revolutional kinetic energyvariation is changed with a shift ratio of i_(c0) as a boundary, asshown in FIG. 12B. Therefore, in a case where the engine serves tocompensate for the required power, a sign of a compensation quantity isneeded to be reversed with the shift ratio of i_(c0) as a boundary.Herein, the compensation quantity when the power required for the gearshift is provided by the engine is calculated. The kinetic energy U ofthe revolutional system of the hybrid-transmission can be expressed inthe following equation.

$\begin{matrix}{{U = {\sum\limits_{j = 1}^{n}{\frac{1}{2}I_{j}\omega_{j}^{2}}}},} & (21)\end{matrix}$Wherein n denotes the number of revolutional members in the hybridtransmission. If the kinetic energy U described in equation (21) isdifferentiated with respect to time, the following equation can beobtained,

$\begin{matrix}{\frac{\mathbb{d}U}{\mathbb{d}t} = {\sum\limits_{j = 1}^{n}{I_{j}{\omega_{j}.}}}} & (22)\end{matrix}$

In equation (22), the revolution speed of each revolutional member dueto the constraint of the revolution speeds of the planetary gearmechanism is given by a linear coupling between engine revolution speedωi and output revolution speed ωo.

$\begin{matrix}{\frac{\mathbb{d}U}{\mathbb{d}t} = {{( {{m_{ii}\frac{\mathbb{d}\omega_{i}}{\mathbb{d}t}} + {m_{oi}\frac{\mathbb{d}\omega_{o}}{\mathbb{d}t}}} )\omega\; i_{i}} + {( {{m_{io}\frac{\mathbb{d}\omega_{i}}{\mathbb{d}t}} + {m_{oo}\frac{\mathbb{d}\omega_{o}}{\mathbb{d}t}}} ){\omega_{o}.}}}} & (23)\end{matrix}$

In equation (23), m_(ii), m_(io), m_(oi), and m_(oo) denotes constantsdetermined according to the specifications of the hybrid transmission.

-   -   dU/dt expressed in equation (23) is a power Pi required for the        shift and dωi/dt in equation (23) is the post-correction target        engine revolution speed, or obtained from equation (11), or        dω_(o)/dt can be obtained from the following equation (24).

$\begin{matrix}{\frac{\mathbb{d}\omega_{o}}{\mathbb{d}t} = {{{b^{\prime}}_{11}T_{R}} + {{b^{\prime}}_{21}T_{E}} + {{b^{\prime}}_{13}T_{1}} + {{b^{\prime}}_{14}{T_{2}.}}}} & (24)\end{matrix}$

In equation (24), b′₂₁, b′₂₂, b′₂₃, and b′₂₄ denote constants determinedaccording to the specifications of the hybrid transmission. Targetengine torque T*EO is corrected as follows to determine engine torquecommand value T*_(E) in order to provide the engine for the powerrequired for the shift.

$\begin{matrix}{{T*_{E}} = {T*_{EO}{+ {\frac{p_{i}}{\omega_{i}}.}}}} & (25)\end{matrix}$

If equation (25) is used, the sign of compensation quantity of the powerrequired for the shift is automatically changed with the shift ratioi_(co) as a boundary. The shift ratio i_(co) is determined usingequation (23). As expressed in the following equation (26), the shiftratio when dU/dt=0 is a kinetic energy minimum gear shift ratio i_(cO).

$\begin{matrix}{i_{co} = {{- \frac{{m_{ii}\frac{\mathbb{d}\omega_{i}}{\mathbb{d}t}} + {m_{oi}\frac{\mathbb{d}\omega_{o}}{\mathbb{d}t}}}{{m_{io}\frac{\mathbb{d}\omega_{i}}{\mathbb{d}t}} + {m_{oo}\frac{\mathbb{d}\omega_{o}}{\mathbb{d}t}}}} = {- {\frac{m_{ii} + {m_{oi}\frac{\mathbb{d}\omega_{o}}{\mathbb{d}\omega_{i}}}}{m_{io} + {m_{oo}\frac{\mathbb{d}\omega_{o}}{\mathbb{d}\omega_{i}}}}.}}}} & (26)\end{matrix}$As expressed in equation (26), kinetic energy minimum shift ratio i_(cO)is dependent upon input revolution acceleration dωi/dt and outputrevolution acceleration dω_(o)/dt. However, during the shift at whichthe power required for the shift becomes large, the following assumptioncan be made:dω _(o) /dω _(i)=0  (27).Using equation (26), kinetic energy minimum gear shift ratio i_(co) maybe the constant.

$\begin{matrix}{i_{co} = {- {\frac{m_{ii}}{m_{io}}.}}} & (28)\end{matrix}$In a case of the hybrid transmission in which an engine clutch which isclutched or released between engine ENG and hybrid transmission, eachvalue of m_(ii), m_(io), m_(oi), and m_(oo) is different dependent uponthe clutch state and release state. Consequently, as appreciated fromequations (26) and (28), kinetic energy minimum shift ratio i_(co) isdifferent depending upon the clutched state of engine clutch.

In the first embodiment of the shift control apparatus, as describedabove with reference to FIG. 7C and FIG. 8 (step S14), if thecombination of target drive (or driving) torque T*_(oO) and targetengine (input revolution acceleration u_(io) is out of realizable regionA, these target drive (driving) torque T*_(oO) and target engine (input)revolution acceleration u_(io) are corrected so as to change the valueswithin realizable region A and to be set as drive torque command valueT*_(oO) and engine (input) revolution acceleration command value u_(i)to contribute to controls of engine ENG and motor/generators MG1 andMG2. Hence, an earlier deterioration of the battery developed in thecase where target drive (driving) torque T*_(oO) and target engine(input) revolution acceleration u_(io) which are out of realizableregion A directly contribute on the controls of engine ENG andmotor/generators MG1 and MG2 can be prevented.

Then, when target drive (driving) torque

T*_(oO) and target engine (input) revolution acceleration u_(io) arecorrected to the values within realizable region A, both signs(polarities) of the corrected drive torque command value T*o and engine(input) revolution acceleration command value u_(i) are not changed fromthose of target drive (driving) torque T*_(oO) and target engine (input)revolution acceleration u_(io). Hence, if post-correction drive torquecommand value T*o and engine (input) revolution acceleration commandvalue u_(i) are used for the controls of engine ENG and motor/generatorsMG1 and MG2, the shift speed (engine (input) revolution acceleration) isnot reversed in the opposite direction that the driver has expected, thesituation in which the input revolution speed change which is oppositeto the driver's expectation from the driving operation occurs can beavoided, and the anxiety such that the shift gives unpleasant feeling tothe driver can be eliminated.

Second Embodiment

FIGS. 13A through 13D and FIG. 14 show a correction processing on thetarget drive (driving) torque and target engine (input) revolutionacceleration of the shift control apparatus in a second embodimentaccording to the present invention. FIGS. 13A through 13D and FIG. 14correspond to the realizable region diagrams and flowchart of FIGS. 7Athrough 7C and FIG. 8.

In the second embodiment, since the structure of the hybridtransmission, the shift control system, and block diagrams dependent onthe shift control function are the same as those of the first embodimentshown in FIGS. 1 through 3, the explanations thereof will herein beomitted. Only the correction method of target drive (driving) torqueT*_(oO) and target engine acceleration u_(io) will be explained withreference to the realizable region diagram in FIGS. 13A through 13D andwith reference to the control program shown in FIG. 14.

In FIGS. 13A, 13B, 13C, and 13D, the target operating point representedby ante-correction target drive (driving) torque T*_(oO) and targetengine (input) revolution acceleration u_(io) are denoted by the whitecircle ? and the command operating point represented by thepost-correction drive torque command value T*o and target engine (input)revolution acceleration u_(i) is denoted by the black circle •. Targetoperating point o shown in FIG. 13A indicates a running state withoutthe shift by a certain target drive (driving) torque T*_(oO) (engine(input) revolution acceleration (d/dt)ωi=0). Thereafter, when theaccelerator pedal is depressed, target operating point o is moved asdenoted by a broken line of FIG. 13B. However, since target operatingpoint o is placed within realizable region A in FIG. 13B, the correctionof target derive torque T*_(oO) and target engine (input) revolutionacceleration u_(io) is not carried out. Thereafter, when targetoperating point o is furthermore moved as denoted by a broken line shownin FIG. 13C, target operating point o is out of realizable region A sothat the combination of target drive (driving) torque T*_(oO) and targetengine (input) revolution acceleration u_(i), which correspond toearliest cannot only be achieved but also does not fall within the ratedpower of the battery. Consequently, the reduction of the life of thebattery is introduced. In this case, target value correcting section103, on the two-dimensional coordinate of drive torque To andtwo-dimensional coordinate of engine (input) revolution acceleration(d/dt)ωi shown in FIG. 13C, derives in the following way commandoperating point • on the basis of target operating point o correspondingto the combination of target drive (driving) torque T*_(oO) and targetengine (input) revolution acceleration u_(io). Then, target valuecorrecting section 103 sets drive torque T*o and engine (input)revolution acceleration u_(i) at this command operating point • as thedrive torque command value and the engine (input) revolutionacceleration command value.

When command operating point • is determined, since a degree ofrequirement of the achievement of target drive (driving) torque T*_(oO)is higher than target engine (input) revolution acceleration u_(io)particularly when such a shift that both of target driver torque T*_(oO)and target engine (input) revolution acceleration u_(io) are abruptlyvaried occurs. Hence, target drive (driving) torque T*_(oO) is notcorrected but is directly set as drive torque command value T*o butengine (input) revolution acceleration u_(io) is corrected. Thus, targetoperating point o which corresponds to the combination of target drive(or driving) torque T*_(oO) and target engine (input) revolutionacceleration u_(io) is moved by a minimal displacement within realizableregion A. At this time, a point • to which above described point ? ismoved by minimal displacement is set as command operating point. In moredetails, a point • which is nearest to target operating point o, whichis within realizable region A, and which is on a line segment (a linesegment by which target drive (or driving) torque T*_(oO) is maintained)passing through target operating point o corresponding to thecombination of target drive (driving) torque T*_(oO) and target engine(input) revolution acceleration u_(io) and denoted by a dot-and-dashline parallel to an engine (input) revolution acceleration axis which isa longitudinal axis of FIG. 13C is the command operating point. Thedrive torque T*o and engine (input) revolution acceleration u_(io) atthis point of is set as the drive torque command value and the engine(input) revolution acceleration command value. Thereby, during the shiftoperation, while compensating for the achievement of target drive(driving) torque T*o whose degree of importance is high, a minimumcorrection of only target engine (input) revolution acceleration u_(io)can move target operating point o to command operating point • withinrealizable operating region A.

When target operating point o corresponding to target drive (driving)torque T*_(oO) and target engine (input) revolution acceleration u_(io)furthermore moved as a broken line shown in FIG. 13D, post-correctionengine (input) revolution acceleration command value indicates a smallvalue as denoted by y₂ derived in the way described with reference toFIG. 13C. Thus, this command value becomes smaller than preset enginerevolution (input) acceleration lower limit set value y_(min). In thisway, if engine (input) revolution acceleration command value u_(i) whichbecomes smaller than lower limit set value y_(min) is allowed, engine(input) revolution acceleration command value u_(i) becomes extremelysmall so that almost no shift occurs. In worst case, engine (input)revolution acceleration command value u_(i) indicates a negative valueand the situation such that a sense of incompatibility of the shift isdeveloped.

To avoid such a worst case, as shown in FIG. 13D, in a case where targetoperating point o is moved, a point of intersection between one of twoboundary lines prescribing realizable region A which is nearer to targetoperating point o (which is called a realizable region boundary line)and a line representing engine revolution (input revolution)acceleration lower limit value y_(min) is set as command operating point•. Drive torque T*o and engine (input) revolution acceleration u_(i) atthis command operating point • is set as the drive torque command valueand the engine (input) revolution acceleration command value. Therefore,the same action and advantage can be achieved, while avoiding engine(input) revolution acceleration command value u_(i) which does notbecome less than engine revolution (input revolution) acceleration lowerlimit set value y_(min), thus, while the sense of incompatibility forthe shift is prevented from occurring, target operating point ? is movedto command operating point ? within the realizable region A with aminimum correction of target drive (driving) torque T*_(oO) and targetengine (input) revolution acceleration u_(io). According to theabove-described correction, since the correction of target drive(driving) torque T*_(oO) and target engine (input) revolutionacceleration u_(io) can be made smoothly and continuously, developmentof unnatural vehicular acceleration shock and the development of theengine revolution speed variation can be prevented.

Target value correcting section 103 executes the above-describedcorrection of target drive (driving) torque T*_(oO) and target engine(input) revolution acceleration u_(io) (determination of drive torquecommand value T*o and engine (input) revolution acceleration u_(i)) inaccordance with the operational flowchart shown in FIG. 14. That is tosay, at a step S30, target value correcting section 103 derivesrealizable region A represented on the two-dimensional coordinate ofdrive torque To and engine (input) revolution acceleration (d/dt)ωishown in FIGS. 13A through 13D in the same process as described at stepS10 shown in FIG. 8 and calculates the two boundary lines prescribingthis region according to equations (8) and (9). At a step S31, targetvalue correcting section 103 derives points of intersections (x₀, y₁)and (x₀, y₂) between a straight line passing target operating point (x₀,y₀) corresponding to the combination of target drive (driving) torque x₀(=T*_(oO)) and target engine (input) revolution acceleration y₀(=u_(io)) shown in FIGS. 13A through 13D and expressed in the followingequation and which is parallel to the longitudinal axis, viz., engine(input) revolution acceleration axis of FIGS. 13A through 13D and thetwo boundary lines prescribing realizable region A as shown in FIGS. 13Athrough 13D (It is noted that y₁<y₂).T_(o)=T*_(oO)  (29).

At a step S32, target value correcting section 103 determines whether y₀is present between y₁ and y₂. If y₀ is present between y₁ and y₂, theroutine goes to a step s33 since the combination of target drive(driving) torque T*_(oO) and target engine (input) revolutionacceleration u_(io) fall within realizable region A as shown in FIGS.13A and 13B. If y₀ is not present between y₁ and y₂ at step S32, theroutine goes to a step S34 since the combination of target drive(driving) torque T*o and target engine (input) revolution accelerationu_(io) is out of realizable region A as shown in FIGS. 13C and 13D.

At step S33 which is selected when the combination of target drive(driving) torque T*_(oO) and target engine (input) revolutionacceleration u_(io) falls within realizable region A, target operatingpoint ? which is the combination of target drive (driving) torque x_(o)(=T*_(oO)) and target engine (input) revolution acceleration y₀(=u_(io)) is directly set as the command operating point. Target drive(driving) torque T*_(oO) is set directly as post-correction target drive(driving) torque command value T*_(o) and target drive engine (input)revolution acceleration u_(io) is directly set as post-correction engine(input) revolution acceleration command value u_(i).

At step S34 which is selected when the combination of target drive (ordriving) torque T*_(oO) and target engine (input) revolutionacceleration u_(io) are out of realizable region A, target valuecorrecting section 103 derives a point of intersection (x₀, y_(c))between the realizable region boundary line nearer to target operatingpoint (x₀, y₀) and the line expressing T_(o)=x₀ as shown in FIGS. 13Cand 13D. It is noted that the point of intersection (x₀, y_(c)) is apoint wherein target drive (driving) torque T*_(oO) is not changed buttarget input revolution acceleration u_(io) is moved to a point of y_(c)which is within realizable region A and which is nearest to y₀. At thenext step S35, equation (19) is used to calculate engine (input)revolution acceleration lower limit set value y_(min).

At the next step S36, target value correcting section 103 determineswhether y_(c) is located nearer to y₀ side than y_(min) as shown in FIG.13C. If with reference to y_(min) y_(c) is located toward y₀ side, asufficient engine (input) revolution acceleration can be obtained (asufficient shift speed can be obtained) so that the routine goes to astep S37. If, as shown in FIG. 13D, y_(c) is not located toward y_(c),the sufficient engine (input) revolution acceleration is not obtainedbut the above-described problems may occur so that the routine goes to astep S38.

At step S37 selected when the sufficient engine (input) revolutionacceleration can be obtained (sufficient shift speed can be obtained),as shown in FIG. 13C, point of intersection (x₀, y_(c)) is set ascommand operating point, drive torque T*o and engine revolution speedu_(i) at this command operating point are set as post-correction drivetorque command value T*_(o) and post-correction engine (input)revolution acceleration command value u_(i). At step S38 selected whenno sufficient engine (input) revolution acceleration is obtained (nosufficient shift speed is obtained), as shown in FIG. 13D, the point ofintersection at which one of the two realizable region boundary lineswhich is nearer to target operating point (x₀, y₀) is intersected withthe line expressing engine (dω_(i)/dt)=y_(min) is set as commandoperating point. At this command operating point, drive torque T*_(o)and engine acceleration u_(i) are set, respectively, as post-correctiondrive torque command value T*_(o) and post-correction engine (input)revolution acceleration command value u_(i).

The polarities (signs) of post-correction drive torque command valueT*_(o) and engine (input) revolution acceleration command value u_(i)are the same as those of target drive (driving) torque T*_(oO) andtarget engine (input) revolution acceleration u_(io) in the same way asdescribed in the first embodiment. Hence, the same action and advantagesas described in the first embodiment can be achieved. While engine(input) revolution acceleration command value u_(i) is not smaller thanengine (input) revolution acceleration (input revolution) lower limitset value y_(min), hence, no sense of incompatibility for the shift isgiven, target operating point (x₀, y₀) can be moved to command operatingpoint • within realizable region A with the minimum correction fortarget drive (driving) torque T*_(oO) and target engine (input)revolution acceleration u_(io) so that the same action and advantages asthe first embodiment can be achieved.

Third Embodiment

FIG. 15 shows an operational flowchart executed by target valuecorrecting section 103 of the shift control apparatus in a thirdpreferred embodiment according to the present invention, viz., thecorrection procedure on target drive (driving) torque and target engine(input) revolution acceleration. In the third embodiment, the structureof the hybrid transmission, the shift control system, and shift controlfunction-dependent block diagram are the same as those shown in FIGS. 1through 3. Hence, these explanations will be omitted herein. Thecorrecting method for only target drive (driving) torque T*_(oO) andtarget engine (input) revolution acceleration u_(io) will be describedhereinbelow on the basis of the control program shown in FIG. 15.

In the second embodiment shown in FIGS. 13A through 13D and FIG. 14,when target operating point ? which corresponds to the combination oftarget drive (driving) torque T*_(oO) and target engine (input)revolution acceleration u_(io) is out of realizable region A, targetdrive (driving) torque T*_(oO) is not corrected so much but targetengine (input) revolution acceleration u_(io) is mainly corrected.However, in the third embodiment, on contrary to this, target engine(input) revolution acceleration u_(io) is not so corrected but targetdrive (driving) torque T*_(oO) is mainly corrected.

The target value correcting section 103 in this embodiment calculatestwo boundary lines prescribing realizable region A expressed on thetwo-dimensional coordinates (refer to FIGS. 13A through 13D) of thedrive torque T*_(o) and engine (input) revolution acceleration (d/dt)ωiat a step S40 shown in FIG. 15, in the same processing as step S30 ofFIG. 14. At the next step S41, target value correcting section 103drives points of intersections (x₁, y₀) and (x₂, y₀) between thestraight line passing through target operating point (x₀, y₀) correspondto target drive (driving) torque x₀ (=T*_(oO)) and engine (input)revolution acceleration y₀ (=u_(io)) and parallel to the drive torqueaxis (lateral axis of FIGS. 13A through 13D) and two realizable regionboundary lines (wherein x₁<x₂)=

$\begin{matrix}{\frac{\mathbb{d}\omega_{i}}{\mathbb{d}t} = {u_{io}.}} & (30)\end{matrix}$

At a step S42, target value correcting section 103 determines whether x₀falls within an intermediate between x₁ and x₂. If x, is determined tobe present between x₁ and x₂, the routine goes to a step S43 since thecombination of target drive (driving) torque T*_(oO) and target engine(input) revolution acceleration u_(io) falls within realizable region A.If x₀ is determined not to fall between x₁ and x₂, since the combinationof target drive (driving) torque T*_(oO) and target engine (input)revolution acceleration u_(io) is out of realizable region A, theroutine goes to a step S44. At step S43 selected when the combination oftarget drive (driving) torque T*_(oO) and target engine (input)revolution acceleration u_(i), is within realizable region A, targetoperating point which is the combination of target drive (driving)torque x₀ (=T*_(oO)) and target engine (input) revolution accelerationy₀(=u_(io)) is set directly to command operating point and target drive(driving) torque T*_(oO) is set directly as post-correction drive torquecommand value T*_(o), and target drive engine (input) revolutionacceleration u_(io) is directly set as post-correction engine (input)revolution acceleration command value u_(i).

At step S44 selected when the combination of target drive (driving)torque T*_(oO) and target engine (input) revolution acceleration u_(io)is out of realizable region A, target value correcting section 103derives the point of intersection (x_(c), y₀) between one of the twoboundary lines prescribing the realizable region which is nearer totarget operating pint (x_(o), y_(o)) and the line expressing(d/dt)ωi=y₀. It is noted that the point of intersection (x_(c), y₀) is apoint with target input revolution acceleration u_(io) unchanged andtarget drive (driving) torque T*_(oO) is moved to a point x_(c) withinrealizable region A which is nearest to x₀. At the next step S45, adrive torque lower limit set value x_(min) is calculated using thefollowing equation.

$\begin{matrix}{X_{\min} = {{Kx} \cdot {\frac{\sigma_{x}}{{\sigma_{x}} + ɛ_{x}}.}}} & (31)\end{matrix}$It is noted that σ_(x) denotes a deviation between target engine (input)revolution speed and actual input revolution speed, ε_(x) denotes apositive constant with σ_(x)=0 continuous for x_(min). Kx denotes apositive constant obtained, for example, by a previously experiments andcomputer simulations.

At the next step S46, target value correcting section 103 determineswhether x_(c) is located toward x₀ side with respect to x_(min). Ifx_(c) is located toward x₀ side with respect to x_(min), the sufficientdrive torque can be obtained and the routine goes to a step S47. Ifx_(c) is not located toward x₀ side, a sufficient drive torque cannot beobtained and the routine goes to a step S48. At step S47 selected whenthe sufficient drive torque is obtained, the point of intersection(x_(c), y₀) is the command operating point and drive torque T*o andengine (input) revolution acceleration u_(io) at this command operatingpoint is set to post-correction drive torque command value T*o andpost-correction engine (input) revolution acceleration command valueu_(i). At step S48 selected when no sufficient drive torque is obtained,a point of intersection between one of the two realizable regionboundary lines which is nearer to target operating point (x₀. y₀) andthe line expressing drive torque To=x_(min). is the command operatingpoint. The drive torque T*o and engine (input) revolution accelerationcommand value u_(i), respectively, at this command operating point, areset to post-correction drive torque command value T*_(o) andpost-correction engine (input) revolution acceleration command valueu_(i).

Hence, post-correction drive torque command value T*o and engine (input)revolution acceleration command value u_(i) have respectively the samepolarities of target drive (driving) torque T*_(oO) and target engineacceleration u_(io) as described in the second embodiment. The sameaction and advantages can be achieved. While drive torque command valueT*o is smaller than predetermined drive torque limit value set valuex_(min), target operating point (x_(o), y_(o)) can be moved to thecommand operating point within realizable region A with minimumcorrection of target drive (driving) torque T*_(oO) and target engine(input) revolution u_(io).

Fourth Embodiment

FIG. 16 shows another type of hybrid transmission in whichmotor/generators MG1 and MG2 are individually and independentlyinstalled as different from motor/generators MG1 and MG2 which isconstituted by compound current two-layer motor 3. That is to say,circular ring shaped stators 3 sl and 3 s 2 are coaxially arranged andfixedly mounted within transmission casing 1, and rotors 3 rl and 3 r 2are revolutionally supported by means of stators 3 sl and 3 s 2.Circular ring shaped stator 3S1 and rotor 3 rl constitute firstmotor/generator MG1 near to engine ENG and circular ring shaped stator 3s 2 and rotor 3 r 2 constitute second motor/generator MG2 which islocated far away from engine ENG.

Motor/generators MG1 and MG2 function as respectively motors inaccordance with a supply current when a current is supplied to ringshaped stators 3 sl and 3 s 2, individually, in an individual direction.When no current is supplied, each generator is acted which develops theelectrical power in accordance with the revolution by means of anexternal force.

When motor/generators MG1 and MG2 are coupled to Ravigneaux typeplanetary gear set 2, rotor 3 r 2 of first motor/generator MG1 iscoupled to sun gear S1 of Ravigneaux type planetary gear set via axle 11and a rotor 3 r 2 of second motor/generator MG2 is coupled to sun gearS2 via axle 12.

In a case where the hybrid transmission is used having theabove-described motor/generators MG1 and MG2 as shown in FIG. 16. acontrol current of motor/generators MG1 and MG2 is required to besupplied to ring shaped stators 3 sl and 3 s 2 individually. Hence, thecontrol system is as shown in FIG. 17 in place of those shown in FIG.12. That is to say, in the case of FIG. 2, a single inverter common toboth motor/generators MG1 and MG2 is only installed. However, in thecase of FIG. 17, an inverter 24 a for ring shaped stator 3 s 1 of thefirst motor/generator MG1 and an inverter 24 b for ring shaped stator 3s 2 is individually installed for ring shaped stator 3 s 2 of secondmotor/generator MG2.

In this embodiment, hybrid controller 21 is shown in the form offunctional block diagram as shown in FIG. 3. In this embodiment,however, the processes in target value correcting section 103 andmotor/generator command value determining section 105 are different fromthat shown in FIG. 3.

The process at target value correcting section 103 is, in the same wayas described in first, second, and third embodiments, such that, in acase where the target operating point corresponding to the combinationof target drive (driving) torque and target engine (input) revolutionacceleration is out of realizable region on the two-dimensionalcoordinate on the drive torque and engine (input) revolutionacceleration, these target drive (driving) torque and/or target engine(input) revolution acceleration are corrected to the drive torquecommand value and engine (input) revolution acceleration command valueon the command operating point within the realizable region. In thispreferred embodiment, the realizable region on the two-dimensionalcoordinates on the drive torque and engine (input) revolutionacceleration is different from realizable region denoted by A shown inFIGS. 6, 7A through 7C, and 13A through 13D, as will be described below.

From the relationship among drive torque To, engine (input) revolutionacceleration (d/dt)ωi, engine revolution speed ωi, output revolutionspeed ωo, running resistance torque T_(R), engine torque T_(E), andbattery charge-and-discharge quantity P_(B), the two-dimensionalcoordinate with the lateral axis taken as drive torque To and thelongitudinal axis taken as engine (input) revolution acceleration(d/dt)ωi, a realizable region which falls within the battery rated poweris represented as A shown in FIG. 6. In this embodiment, a region BC ofdrive torque and engine (input) revolution acceleration by means of atorque mechanically generable through motor/generators MG1 and MG2 isderived as shown in FIG. 18 and a region D shown in FIG. 19 which is anoverlapped region between region BC and region A is called realizableregion.

Before explanation of the derivation of region BC, engine (input)revolution acceleration of the hybrid transmission is expressed as inequation (11) and the drive torque is expressed as in equation (12).I_(c)b₂₄×equation (11)−b₁₄×equation (12).

$\begin{matrix}\begin{matrix}{{{I_{c}b_{24}\frac{\mathbb{d}\omega_{i}}{\mathbb{d}t}} - {b_{14}T_{0}}} = {{( {{I_{c}b_{24}b_{11}} - {I_{c}b_{14}b_{21}} + 1} )T_{R}} +}} \\{{{I_{c}( {{b_{24}b_{12}} - {b_{14}b_{22}}} )}T_{E}} +} \\{{I_{c}( {{b_{24}b_{13}} - {b_{14}b_{23}}} )}{T_{1}.}}\end{matrix} & (32)\end{matrix}$

In addition, the following equation can be derived fromI_(c)b₂₃×equation (11)−b₁₃×equation (12).

$\begin{matrix}\begin{matrix}{{{I_{c}b_{23}\frac{\mathbb{d}\omega_{i}}{\mathbb{d}t}} - {b_{13}T_{o}}} = {{( {{I_{c}b_{23}b_{11}} - {I_{c}b_{13}b_{21}} + 1} )T_{R}} +}} \\{{I\;{c( {{b_{23}b_{12}} - {b_{13}b_{22}}} )}T_{E}} +} \\{{I_{C}( {{b_{23}b_{14}} - {b_{13}b_{24}}} )}{T_{2}.}}\end{matrix} & (33)\end{matrix}$

Using equation (32), from the torque range generable mechanically bymotor/generator MG1, the drive torque mechanically generable torque ofmotor/generator and a region B of engine (input) revolution accelerationcan be obtained from FIG. 18. In addition, using equation (33), from atorque range that second motor/generator MG2 mechanically generable, aregion C of the drive torque mechanically generable by secondmotor/generator and engine (input) revolution acceleration can beobtained as shown in FIG. 18. In a case where the independent twomotor/generators MG1 and MG2 are used, a region B is uniquely determinedwithout exception from the revolution speed of the presentmotor/generator MG1 and region C is uniquely determined withoutexception from the revolution speed of the present motor/generator MG2.It is noted that a region on which region B and region C are overlappedis assumed to be BC.

Then, as shown in FIG. 19, a realizable region D between drive torqueand engine revolution speed is assumed on which region A and region BCare overlapped is assumed. In each of the above-described first throughthird embodiments, since motor/generators are constituted by thecomposite current two-layer motor 3, region BC is not obtained. Adependent relationship is present as expressed in equation (16) betweenrevolution speed of motor/generator MG2, maximum torque T_(1max) ofmotor/generator MG1, and maximum torque T_(2max) of secondmotor/generator MG2. This dependent relationship causes the dependentrelationship between regions B and C, as shown in FIG. 20, under therevolution speed of present motor/generator MG1 and revolution speed ofpresent motor/generator MG2, as shown in FIGS. 20A, 20B, and 20C. RegionB is narrower as T_(2max) becomes smaller (T_(1max) becomes larger) andwider as T_(2max) becomes larger, (T_(1max) is smaller). On the otherhand, region C becomes wider as T_(2max) becomes smaller (T_(1max)becomes larger), as shown in FIGS. 20A, 20B, and 20C. As describedabove, since region B and region C are variable, region BC on which bothare overlapped is variable. It is difficult to include this region BC inrealizable region D, as shown in FIG. 19.

Hereinafter, the process by means of target value correcting section 103shown in FIG. 3 is executed in accordance with the flowchart shown inFIG. 21 in place of the program shown in FIG. 8. At a step S250, targetvalue correcting section 103 determines whether target operating pointwhich is the combination of target drive (driving) torque x₀ (=T*₀₀) andtarget engine (input) revolution acceleration y₀ (=u_(io)) falls withinrealizable region D described above so as to determine whether targetengine torque T*_(oO) and target engine (input) revolution accelerationu_(io) are feasible.

The determination of feasibility is based on the determination ofwhether target drive (driving) torque T*_(oO) and target engine (input)revolution acceleration u_(io) are feasible when the following threeconditions are satisfied.

(Condition 1)

The battery-and-discharge quantity when target drive (driving) torqueT*_(oO) and target engine acceleration u_(io) are substituted intoequation (7) is equal to or below the battery rated power.

(Condition 2)

T₁ when target drive (driving) torque T*_(oO) and target revolutionacceleration u_(io) are substituted into equation (32) is a torquemechanically generable at the present revolution speed of the firstmotor/generator MG1.

(Condition 3)

T2 when target drive (driving) torque T*_(oO) and target engine (input)revolution acceleration u_(io) are substituted into equation (33) is amechanically generable torque at the present revolution speed of themotor/generator MG2.

In a case where target drive (driving) torque T*_(oO) and target engine(input) revolution acceleration u_(io) are determined to be feasible(realizable) at step S50, at a step S51, target value correcting section103 sets the target operating point which is a combination of targetdrive (driving) torque x₀ (=T*_(oO)) and target engine (input)revolution acceleration y₀ (=u_(io)) directly as the command operatingpoint, target drive (driving) torque T*_(oO) is set directly aspost-correction drive torque command value T*_(o), target drive engine(input) revolution acceleration u_(io) is directly set aspost-correction engine acceleration command value u_(i).

In a case where target drive (driving) torque T*_(oO) and target engine(input) revolution acceleration u_(io) are determined not to berealizable at step S50, at a step S52, from among points ofintersections at which a line segment connecting an origin and thetarget operating point (x₀, y₀) is intersected with boundary lines oforigin A, origin B, and origin C, one point of intersection which iswithin the realizable region D and which is nearest to target operatingpoint is the command operating point, the drive torque T*o and engine(input) revolution acceleration u_(i) are respectively set aspost-correction drive torque command value T*o and as post-correctionengine (input) revolution acceleration value u_(i).

In this embodiment, the process carried out by motor/generator torquecommand value determining section 105 shown in FIG. 3 is such that, inthe same manner as described in each embodiment, when targetmotor/generator torques T*₁₀ and T*₂₀ from motor/generator torquedistributing section 104 are in excess of mechanically output enabletorque range or in excess of the battery rated power (is out of operableregion), these are output enable range and a value within the batteryrated power, these are corrected to values thereof within output enabletorque range and battery rated power to form motor/generator torquecommand values T*₁ and T*₂. Thereby, motor/generator torque commandvalue determining section 105 functions as the protection functionagainst the deterioration of motor/generators MG1 and MG2, earlierdeterioration of battery, performs a protection function describedabove, and performs a fail safe function.

Hence, also in this embodiment, motor/generator torque command valuedetermining section 105 in accordance with a determination result ofstep S20 shown in FIG. 9, in details, in accordance with thedetermination of whether motor/generator torques T*₁₀ and T*₂₀ arewithin the operable region or are out of the operable region performsthe same process as step S21 and step S22. The determination method atstep S20 at which the contents of processes of any step should beexecuted is different. Hereinafter, the details thereof will herein bedescribed. When this determination is carried out, in other words, whentarget motor/generator torques T*₁₀ and T*₂₀ are determined to fallwithin operable region. When the determination whether it is out of theregion, this determination is made on the basis of regional diagramshown in FIG. 22.

It is noted that FIG. 22 shows the regional diagram used in thisembodiment. In FIG. 22, the lateral axis denotes a torque T, of firstmotor/generator torque MG1 and the longitudinal axis denotes a torque T₂of the second motor/generator MG2 so that the two-dimensionalcoordinates are formed. On the two-dimensional coordinates, an operableregion FX which can achieve toques of first and second motor/generatorsMG1 and MG2 is shown. The region FA and region FC are the same as thosedescribed with reference to FIG. 10. and the duplicate explanation willherein be omitted.

Next, to derive a mechanical operable region of independent twomotor/generators MG1 and MG2, in a case of the hybrid transmissionhaving independent two motor/generators MG1 and MG2, an operable rangeof the torque of first motor/generator MG1 is uniquely determinedaccording to the revolution speed of motor/generator MG1 and theoperable range of the torque of the second motor/generator MG2 isuniquely determined according to the revolution speed of motor/generatorMG2. Hence, using the relationship between revolution speeds ω₁ and ω₂of first and second motor/generators MG₁ and MG₂ and maximum torquesT_(1max) and T_(2max) of first and second motor/generators MG1 and MG2,maximum torque T_(1max) of first motor/generator MG1 is obtained fromthe present revolution speed ω₁ of first motor/generator MG1 and maximumtorque T_(2max) of second motor/generator MG2 is obtained from thepresent revolution speed ω₂ Of second motor/generator MG2.

From these motor/generator maximum torques T_(1max) and T_(2max), amechanical operable region FB of motor/generators MG1 and MG2 isobtained as shown in FIG. 22. In the case of the hybrid transmissionhaving independent two motor/generators MG1 and MG2, operable region FBis a rectangular shape. An overlapped area between region FB and regionFC are operable region FX of motor/generators MG1 and MG2.

On the basis of FIG. 22, the target value correcting section 103determines whether target motor/generator torques T*₁₀ and T*₂₀ arewithin operable region FX or out of operable region FX. When thefollowing four conditions are satisfied, it can be determined thatmotor/generator torques T*₁₀ and T*₂₀ are within operable region FX.

(Condition I)

In FIG. 23A, battery charge-and-discharge quantity Obtained bysubstituting target motor/generator torques T*₁₀ and T*₂₀ into equation(15) is equal to or lower than battery rated power.

(Condition II)

In FIG. 22A, target motor/generator torque T*₁₀ is present within arange of maximum torque T_(1max) of motor/generator MG1 obtained fromthe present revolution speed ω₁ of motor/generator MG1.

(Condition III)

In FIG. 23B, target motor/generator torque T*₂₀ is present within arange of maximum torque T_(1max) of motor/generators MG1 obtained fromthe present revolution speed W2 of motor/generator MG2

(Condition IV)

If b₁₁T_(R)+b₁₂T_(E)+b₁₃T*₁₀+b₁₄T*₂₀≦0, target motor/generator torquesT*₁₀ n T*₂₀ satisfy the relationship of equation (17) described aboveand if b₁₁T_(R)+b₁₂T_(E)+b₁₃T*₁₀+b₁₄T*₂₀≦0. both of targetmotor/generator torques T*₁₀, T*₂₀ satisfy the relationship of equation(18).

In this embodiment, when the above-described four conditions aresatisfied at step S20 in FIG. 9, target motor/generator torques T*₁₀ andT*₂₀ are within operable region FX and the step S21 of the same drawingis executed. When, at step S20 of FIG. 9, the above-described fourconditions are not satisfied, the step S22 is executed sincemotor/generator torques T*₁₀, T*₂₀ are out of operable region FX.Therefore, the same action and advantages as described in each of thefirst through third embodiment can be achieved.

Fifth Embodiment

FIG. 24 shows a correction procedure of target drive (driving) torqueand target engine (input) revolution acceleration in place of FIG. 21and to be executed in a fifth preferred embodiment of the shift controlapparatus according to the present invention.

In this embodiment, the hybrid transmission is the same as FIG. 16 andthe shift control system is the same as FIG. 17. Furthermore, hybridcontroller 21 in FIG. 16 is the same as FIG. 3 when the functional blockdiagram is shown. Target value correcting section 103 executes theflowchart of FIG. 24 in place of FIG. 21.

Herein, a processing of the flowchart shown in FIG. 24 executed bytarget value correcting section 103 will be described below.

At a step S60, in the same way as described at step S50 shown in FIG.21, depending upon whether the target operating point which is thecombination of target drive (driving) torque x₀ (=T*_(oO)) and targetengine (input) revolution acceleration y₀ (=u_(io)) falls withinrealizable region D shown in FIG. 19, a kind of check by means of targetvalue correcting section 103 is made as to whether target drive(driving) torque T*_(oO) and target engine (input) revolutionacceleration u_(io) is feasible.

If, at step S60, the determination is made that target drive (driving)torque T*_(oO) and target engine (input) revolution acceleration u_(io)are determined to be feasible, the routine goes to a step S61. At stepS61, the target operating point is set directly as the command operatingpoint which is the combination of target drive (driving) torquex₀(=T*_(oO)) and target engine (input) revolution acceleration y₀(=u_(io)), target drive (driving) torque T*_(oO) is directly set aspost-correction drive torque command value T*O, and target engine(input) revolution acceleration u_(io) is directly set aspost-correction engine (input) revolution acceleration command valueu_(i). In a case where, at step S60, if determination is made thattarget drive (driving) torque T*_(oO) and target engine (input)revolution acceleration u_(io) are not feasible, the routine goes to astep S62. In the same way as described with reference to step S34 inFIG. 14, target value correcting section 103 derives points ofintersections (x₀, y_(c)) between boundary lines of regions A, B, and C(refer to FIGS. 18 and 19) which are nearest to target operating point(x₀, y₀) within realizable region D and a line expressing To=x₀. It isnoted that point of intersection (x₀, y_(c)) is a point at which targetdrive (driving) torque T*_(oO) is left unchanged and target inputrevolution acceleration u_(io) is moved to a point y_(c) withinrealizable region D which is nearest to y₀.

At the next step S63, target value correcting section 103 calculatesengine (input) revolution acceleration lower limit set value y_(min) inthe same way as described with reference to step S35 of FIG. 14. At thenext step S64, in the same way as step S36 in FIG. 14, target valuecorrecting section 103 determines whether y₀ falls within y₀ side withrespect to y_(min). If y_(c) is located at y₀ side with respect toy_(min), the sufficient engine (input) revolution acceleration (thesufficient shift speed) can be obtained. Thus, the routine goes to astep S66. If y_(c) is not located toward y₀ side with respect toy_(min), the routine goes to a step S66.

At a step S65 selected when the sufficient engine (input) revolutionacceleration is obtained (the sufficient shift speed is obtained), inthe same way as step S37 in FIG. 14, the point of intersection (x₀,y_(c)) is set as the command operating point, the drive torque T*o andengine (input) revolution acceleration u_(i) at this command operatingpoint are set as post-selection drive torque command value T*o andpost-correction engine input revolution acceleration command valueu_(i). At the step S66 selected when the engine (input) revolutionacceleration cannot be obtained sufficiently (a sufficient shift speedis not obtained), in the same way as described with reference to stepS38 in FIG. 14, a point of intersection which is nearest to the targetoperating point (x₀, y₀) within realizable region D from among the pointof intersections at which the boundary lines of regions A, B, and C(refer to FIGS. 18 and 19) are intersected with the line representingthe engine (input) revolution acceleration (d/dt)ωi=y_(min) is set asthe command operating point, drive torque T*o and engine (input)revolution acceleration u_(i) at this command operating point are set aspost-correction drive torque command value T_(o*) and post-correctionengine (input) revolution acceleration command value u_(i).

Hence, the post-correction drive torque command value To* and engine(input) revolution acceleration command value u_(i) have the samepolarities as those of the target drive (driving) torque T*_(oO) andtarget engine (input) revolution acceleration u_(io). The same actionand advantages as described in each of the previously describedembodiments can be achieved. While the sense of incompatibility with theshift is prevented from occurring (engine revolution (input revolution)acceleration command value u_(i) does not become a value lower than(predetermined) engine revolution (input revolution) acceleration lowerlimit value y_(min), target operating point (x₀, y₀) can be moved to thecommand operating point within realizable region D with minimumcorrection of target drive (driving) torque T*_(oO) and target engine(input) revolution acceleration u_(io). Consequently, the same actionand advantages as described in each of the first through fourthembodiments can be achieved.

Sixth Embodiment

FIG. 26 shows a correction processing of target drive (driving) torqueand target engine (input) revolution acceleration in place of FIG. 21 tobe executed by the shift control apparatus of the hybrid transmission ina sixth preferred embodiment according to the present invention. Thehybrid transmission in the sixth embodiment is the same as that shown inFIG. 16 and the shift control system is the same as that shown in FIG.17. Furthermore, hybrid controller 21 in FIG. 16 is the same as depictedin FIG. 3. However, target value correcting section 103 in thisembodiment is different from that shown in FIG. 3 in that target valuecorrecting section 103 in this embodiment executed the flowchart shownin FIG. 25 in place of that shown in FIG. 21. Hereinafter, theprocessing of flowchart that target value correcting section 103executes will be described below with reference to the flowchart of FIG.25.

At a step S70, target value correcting section 103 determines whetherthe target operating point which is the combination of target drive(driving) torque x₀(=T*_(oO)) and target engine (input) revolutionacceleration y₀(=u_(io)) falls within realizable region D shown in FIG.19 so as to determine whether target drive (driving) torque T*_(oO) andtarget engine (input) revolution acceleration u_(io) are feasible.

In a case where, at step S70, target value correcting section 103determines that target drive (driving) torque T*_(oO) and target engine(input) revolution acceleration u_(io) are feasible, at a step S71, inthe same way as contents of step S51 shown in FIG. 21, the targetoperating point which is the combination of target drive (driving)torque x₀ (=T*_(oO)) and target revolution acceleration y₀ (=u_(io)) isset directly as the command operating point, target drive (driving)torque T*_(oO) is directly set as post-correction drive torque commandvalue T*o, and target drive engine (input) revolution accelerationu_(io) is directly set as post-correction engine (input) revolutionacceleration command value u_(i).

In a case where, at step S70, target value correcting section 103determines that target drive (driving) torque T*_(oO) and target engine(input) revolution acceleration u_(io) are not feasible, the routinegoes to a step S72. AT step S72, in the same way as described in stepS44 shown in FIG. 15, target value correcting section 103 derives apoint of intersection (x_(c), y₀) between one of the boundary lines ofregions A, B, and C (refer to FIGS. 18 and 19) which is nearest totarget operating point (x₀, y₀) and which is within realizable region Dand a line expressing (d/dt)ωi=y₀.

Next, at a step S74, target value correcting section 103 determineswhether x_(c) is located toward x₀ side with respect to x_(min), in thesame way as described at step S46 shown in FIG. 15. If x_(c) is locatedtoward x₀ side with respect to x_(min), the drive torque cansufficiently be obtained and the routine goes to a step S75. If x_(c) isnot located toward x₀ side with respect thereto, the sufficient drivetorque cannot be obtained so that the routine goes to a step S76.

At step S75 selected when the sufficient drive torque is obtained, inthe same manner as the step S41 of FIG. 15, point of intersection(x_(c), y₀) is set as the command operating point, drive torque T*o andengine (input) revolution acceleration u_(i) is set as post-correctiondrive torque command value T*_(o) and post-correction engine (input)revolution acceleration command value u_(i). On the other hand, at stepS76 selected when the sufficient drive torque cannot be obtained, in thesame way as described at step S38 shown in FIG. 13, point ofintersection which is nearest to target operating point (x₀, y₀) withinrealizable region D from among the points of intersections between theboundary lines of regions A, B, and C (refer to FIGS. 18 and 19) and aline expressing drive torque To=x_(min) is set as the command operatingpoint. Drive torque T*_(o) and engine (input) revolution accelerationu_(i) at this command operating point are set, respectively, aspost-correction drive torque command value T*o and post-correctionengine (input) revolution acceleration command value u_(i).

Hence, the polarities (signs) of post-correction drive torque commandvalue T*_(o) and post-correction engine (input) revolution accelerationcommand value u_(i) are the same as those of target drive (driving)torque T*_(oO) and target engine (input) revolution acceleration u_(io).Thus, the same action and advantages as those of each of the firstthrough fifth embodiments can be achieved. While preventing drive torquecommand value T*_(o) from becoming lower than drive torque lower limitvalue x_(min), target operating point (x₀, y₀) can be moved to thecommand operating point within realizable region D with minimumcorrection of target drive (driving) torque T*_(oO) and target engine(input) revolution acceleration u_(io).

Various changes and modifications may be made without departing from thescope and sprit of the present invention which is defined in theappended claims.

The entire contents of a Japanese Patent Application No. 2003-100773(filed in Japan on Apr. 3, 2003) are herein incorporated by reference.The scope of the invention is defined with reference to the followingclaims.

1. A shift control apparatus for a hybrid transmission, comprising: aplurality of revolutional members which are enabled to be arranged on apredetermined lever diagram; a differential unit having two degrees offreedom such that if revolution states of two revolutional members ofthe plurality of revolutional members are determined, the revolutionalstates of the other revolutional members of the plurality ofrevolutional members are determined, an input of a main power source(ENG), an output to a drive system, and a plurality of motor/generators(MG1, MG2) are coupled to the respective revolutional members of thedifferential unit to adjust a power from the motor/generators in such amanner that a shift ratio between the main power source and the drivesystem is varied continuously; a target drive torque calculating sectionthat calculates a target drive torque (T*_(oO)) to the drive system inaccordance with a driving condition; a target input revolution speedcalculating section that calculates a target input revolution speed(ω*_(E)) of one of the revolutional members which is coupled to the mainpower source (ENG); a target input revolution acceleration calculatingsection that calculates a target input revolution acceleration (u_(io))to converge an actual input revolution (ωi) into the target inputrevolution speed (ω*i); and a target value correcting section thatcorrects at least one of the target drive torque (T*hd oO) and thetarget input revolution (u_(io)) to be a value within a realizableregion to be set as a drive torque command value (T*_(oO)) and an inputrevolution acceleration command value (u_(io)) in such a manner thatpolarities of the target drive torque (T*_(oO)) and the target inputrevolution acceleration (u_(io)) are left unchanged, wherein in a casewhere a combination of the target drive torque with the target inputrevolution acceleration falls out of a realizable region ontwo-dimensional coordinates of the drive torque and the input revolutionacceleration related to a combination of the drive torque and the inputrevolution acceleration which is feasible in a state of the presentmotor/generators, a battery for the motor/generators (MG1, MG2), and themain power source, the target value correcting section is configured tomake the drive torque command value (T*o) and the input revolutionacceleration command value (u_(i)) contribute to controls of the mainpower source and the motor/generators (3) in place of the target drivetorque (T*_(oO)) and the target input revolution acceleration (u_(io)).2. A shift control apparatus for a hybrid transmission as claimed inclaim 1, wherein the target value correcting section corrects only thetarget input revolution acceleration without the correction of thetarget drive torque when correcting at least one of the target drivetorque (T*o) and the target input revolution acceleration (u_(i)).
 3. Ashift control apparatus for a hybrid transmission as claimed in claim 1,wherein the target value correcting section corrects the target inputrevolution acceleration (u_(io)) not to become lower than apredetermined input revolution acceleration lower limit set value(y_(min)) and to be set as the input revolution acceleration commandvalue when correcting at least one of the target drive torque and thetarget input revolution acceleration and corrects the target drivetorque (T*_(oO)) in such a manner that its correction quantity is to bea minimum to set the drive torque command value (T*o).
 4. A shiftcontrol apparatus for a hybrid transmission as claimed in claim 1,wherein the target value correcting section corrects only the targetdrive torque without correction of the target input revolutionacceleration when correcting at least one of the target drive torque andthe target input revolution acceleration to provide the drive torquecommand value (T*o) and the input revolution acceleration command value(u_(i)).
 5. A shift control apparatus for a hybrid transmission asclaimed in claim 1, wherein the target value correcting section correctsthe target drive torque not to be lower than a predetermined drivetorque lower limit set value (X_(min)) and sets the corrected targetdrive torque as the target torque command value and corrects the targetinput revolution acceleration in such a manner that its correctionquantity is to be minimum and sets the corrected input target revolutionacceleration to the input revolution acceleration command value (u_(i)).6. A shift control apparatus for a hybrid transmission as claimed inclaim 1, wherein the target value correcting section derives twoboundary lines prescribing the realizable region on the two-dimensionalcoordinates of drive torques (To) and the engine (input) revolutionacceleration {(d/dt)dωi} on the basis of a battery rated power(P_(BMAX)), a drive torque (To), the engine (input) revolutionacceleration (d/dt)ωi, a running resistance torque (T_(R)), an enginetorque (T_(E)), and specifications of the hybrid transmission; derives atarget operating point which is a combination of the target drive torquex_(o) (T*_(oO)) and the target input revolution acceleration Y₀(=u_(io)), a straight line passing through an origin of thetwo-dimensional coordinates and the target operating point, and pointsof intersections (x₁, y₁) and (x₂, y₂) at which the straight line isintersected with the two boundary lines, wherein x₁<x₂, and determineswhether x_(o) (=T*_(oO)) falls between x coordinate (x₁) of one boundaryline and x coordinate (x₂) of the other of the two boundary lines.
 7. Ashift control apparatus for a hybrid transmission as claimed in claim 6,wherein, when determining that x₀ (=T*_(oO)) falls between x₁ and x2,the target value correcting section determines that the target drivetorque x₀ (=T*_(oO)) and the target input revolution acceleration y₀(=u_(io)) falls within the realizable region (A) and sets the targetdrive torque x₀ (=T*_(oO)) and the target engine (input) revolutionacceleration y₀ (=u_(io)) directly as a post-correction drive torquecommand value (T*o) and as a post-correction engine revolutionacceleration command value (u_(i)).
 8. A shift control apparatus for ahybrid transmission as claimed in claim 7, wherein, when determiningthat x₀ (=T*_(oO))does not fall within an interspace of thetwo-dimensional coordinates x₁ and x₂, the target value correctingsection determines that the target drive torque x₀(=T*_(oO)) and thetarget input revolution acceleration y₀ (=u_(io)) are out of therealizable region (A), sets one of the points of intersections (x₁, y₁)and (x₂, y₂) which is nearer to the target operating point (x₀, y₀) as acommand operating point, and sets the target drive torque (T*_(oO)) asthe post-correction drive torque command value (T*_(o)) and thepost-correction input revolution acceleration command value (u_(i)). 9.A shift control apparatus for a hybrid transmission as claimed in claim8, wherein the shift control apparatus further comprises amotor/generator torque distributing section that determines targettorques (T*₁₀ and T*₂₀) of the motor/generators (MG1 and MG2) to achievethe post-correction drive torque command value (T*o) and post-correctioninput revolution acceleration command values (u₁).
 10. A shift controlapparatus for a hybrid transmission as claimed in claim 9, wherein theshift control apparatus further comprises a motor/generator torquecommand value determining section that determines motor/generator torquecommand values (T*₁ and T*₂) to those values within an output enabledtorque range by correcting the target motor/generator torques (T₁₀* andT₂₀*) to values thereof within an output enabled torque range in a casewhere the target motor/generator torques (T*₁₀ and T*₂₀) are in excessof the mechanically output enabled torque range or in a case where thetarget motor/generator torques (T*₁₀ and T*₂₀) are in excess of abattery rated power when they are realized.
 11. A shift controlapparatus for a hybrid transmission as claimed in claim 10, wherein themotor/generator torque command value determining section determineswhether the target motor/generator torques (T*₁₀ and T*₂₀) are withinthe mechanically output enabled torque range and within an operableregion that is not in excess of a battery rated power when these targetmotor/generator torques (T*₁₀ and T*₂₀) are realized.
 12. A shiftcontrol apparatus for a hybrid transmission as claimed in claim 11,wherein, on two-dimensional coordinates of the motor/generators (MG1,MG2) torques (T₁ and T₂), the operable region (FX) is an overlappedregion of a region of FA prescribing the drive torque and enginerevolution speed which falls within a battery rated power from a rangeof a battery charge-and-discharge quantity (P_(B)), a region of FBprescribing a mechanically operable region of the motor/generators, andof a region of FC prescribing a torque range of motor/generators (MG1and MG2) when the target motor/generator torques (T*₁₀ and T*₂₀) arecorrected, to prevent the engine revolution acceleration fromapproaching to zero than a predetermined input revolution limit setvalue y_(min), the engine revolution acceleration is a value toward theengine revolution acceleration side when the target motor/generatortorques (T*₁₀ and T*₂₀) are achieved before correction.
 13. A shiftcontrol apparatus for a hybrid transmission as claimed in claim 12,wherein the motor/generator torque command value determining sectiondetermines whether the target motor/generator torques (T*₁₀ and T*20)falls within the operable region (FX) depending upon whetherpredetermined three conditions are satisfied.
 14. A shift controlapparatus for a hybrid transmission as claimed in claim 13, wherein themotor/generator torque command value determining section sets directlythe target motor/generator torques (T*₁₀, T*₂₀) as motor/generatortorque command values (T*₁, T*₂) without correction when the targetmotor/generator torques (T*₁₀, T*₂₀) are determined to fall within theoperable region (FX).
 15. A shift control apparatus for a hybridtransmission as claimed in claim 14, wherein the motor/generator torquecommand value determining section corrects the target motor/generatortorques T*₁₀, T*₂₀ to fall within the operable region (FX) in such amanner that a variation in the drive torque provides a minimum, thecorrected target motor/generator torques being directly set aspost-correction motor/generator torque command values T*₁, T*₂.
 16. Ashift control apparatus for a hybrid transmission as claimed in claim15, wherein, when an ante-correction operating point corresponding tothe target motor/generator torques (T*₁₀, y₂₀) is out of the operableregion of FX and an equi-driving torque straight line passing throughthe ante-correction operating point is not intersected with the operableregion (FX), the corrections for target motor/generator torques T₁, T₂are made in such a manner that an operating point (●) which is withinthe operable region (FX) and nearest to the equi-driving torque straightline passing through the ante-correction operating point is set to be apost-correction operating point, the motor/generator torques (T₁, T₂) atthe post-correction operating point being set to be post-correctionmotor/generator torque command values T*₁ and T*₂.
 17. A shift controlapparatus for a hybrid transmission as claimed in claim 13, wherein thepredetermined three conditions are that a battery charge-and-dischargequantity P_(B) obtained by substituting T*₁₀ and T*₂₀ into equation ofP_(B)=ω₁T₁ _(+ω) ₂T₂; the target motor/generator torque T*₁₀ is smallerthan a torque maximum value T_(1max) of the motor generator MG1 obtainedsubstituting T*₂₀ into equation of T_(1max)=f2(T_(2max), ω₁, ω₂); and,if b₁₁T_(R)+b₁₂T_(E)+b₁₃T*₁₀+b₁₄T*₂₀≧0, the target motor generatortorques T*₁₀ and T*₂₀ satisfy a relationship of an equation ofb₁₁T_(R)+b₁₂T_(E)+b₁₃T₁+b₁₄T₂≧y_(min) and, ifb₁₁T_(R)+b₁₂T_(E)+b₁₃T*₁₀+b₁₄T*₂₀≧0, the target motor/generators T*₁₀,T*₂₀ satisfies the following equationb₁₁T_(R)+b₁₂T_(E)+b₁₃T₁+b₁₄T₂≧y_(min), wherein T_(R) denotes a runningresistance, T₁ and T₂ denote torques of the respective motor/generators,T_(E) denotes an engine torque, b₁₁, b₁₂, b₁₂, and b₁₄ have thefollowing relationship of dωi/dt (i=1, 2)=b₁₁T_(R)+b₁₂T_(E)+b₁₃T₁+b₁₄T₂.18. A shift control apparatus for a hybrid transmission as claimed inclaim 2, wherein the target value correcting section, on two-dimensionalcoordinates of the drive torque (To) and the input revolutionacceleration {(d/dt)ωi}, determines a command operating point (●) on thebasis of a target operating point (o) which corresponds to a combinationof the target drive torque (T*_(oO)) and the target input revolutionacceleration (u_(io)) and, when a gear shift occurs such that bothtarget driving torque (T*_(oO)) and target input revolution acceleration(u_(io)) are abruptly varied, the target driving torque T_(oO) is notcorrected but is directly set to a drive torque command value (T*o) andonly the target input revolution acceleration command value (u_(io)) iscorrected in such a manner that the target operating point (o)corresponding to the combination between the target drive torque(T*_(oO)) and the target input revolution acceleration (u_(io)) is movedwith a minimal displacement within the realizable region (A) to acommand operating point (●) which corresponds to the combination of thedrive torque command value (T*_(o)) and the input engine revolutionacceleration command value (u_(i)).
 19. A shift control apparatus for ahybrid transmission as claimed in claim 18, wherein a point (●) on thetwo-dimensional coordinates which passes through a target operatingpoint (o) which corresponds to the target drive torque (T*_(oO)) and thetarget input revolution acceleration (u_(io)) and on a line segmentwhich is parallel to longitudinal axis representing the enginerevolution acceleration, which is within the realizable region, andwhich is nearest to the target operating point, the drive torque (T*o)and engine revolution acceleration (u_(i)) being set to be the drivetorque command value (T*) and engine revolution acceleration commandvalue (u_(i)).
 20. A shift control apparatus for a hybrid transmissionas claimed in claim 19, wherein, when the post-correction inputrevolution acceleration command value (u_(i)) is smaller than the presetinput revolution acceleration limit set value (y_(min)), a point ofintersection between one of two boundary lines prescribing therealizable region A which is nearer to the target operating point (o)and a line representing the input revolution acceleration lower limitset value y_(min) is (●), the drive torque (T*o) and the enginerevolution acceleration (u_(i)) at the command operating point are setto be the drive torque command value and input revolution accelerationcommand value.
 21. A shift control apparatus for the hybrid transmissionas claimed in claim 4, wherein the target value correcting sectiondetermines points of intersections (x₁, y₀) and (x₂, y₀) between astraight line passing through a target operating point (x₀, y₀) whichcorresponds to a combination between the target drive torque x₀(=T*_(oO)) and the engine revolution acceleration Y₀ (=u_(i)) and whichis parallel to a drive axis of a lateral axis of the two-dimensionalcoordinates with the input revolution acceleration as a longitudinalaxis and two boundary lines prescribing the realizable region (A) anddetermines whether x₀ (=T*_(oO)) falls between a point of x₁ and theother point of x₂ wherein x₁<x₂.
 22. A shift control apparatus for thehybrid transmission as claimed in claim 21, wherein the target valuecorrecting section determines a point of intersections (x_(c), y₀)between one of the two boundary lines prescribing the realizable regionwhich is nearer to the target operating point and a line expressing(d/dt)ωi=y₀, the point of intersection (x_(c), y₀) being moved with thetarget input revolution acceleration (u_(io)) left unchanged and thetarget drive torque (T*_(oO)) moved to a point (x_(c)) within therealizable region which is nearest to (x₀)., calculates the drive torquelower limit set value (x_(min)) on the basis of a deviation between atarget engine revolution speed and actual engine revolution speed, anddetermines whether, with x_(min) as a reference, x_(c) is located towardx₀ side.
 23. A shift control apparatus for the hybrid transmission asclaimed in claim 22, wherein the target value correcting section setsthe point of intersection (x₀, y₀) as a command operating point whendetermining that the point (x_(c)) is located toward x₀ side with(x_(min)) as the reference, the drive torque (T*_(o)) and enginerevolution acceleration (u_(i)) at the command operating point being setas a post-correction drive torque command value (T*o) and apost-correction engine revolution acceleration command value (u_(i)) andwhen determining that the point (x_(c)) is not located toward x₀ sidewith (x_(min)) as the reference, a point of intersection between one ofthe two boundary lines prescribing the realizable region which is nearerto the target operating point (x₀, y₀) and a line expressing the drivetorque T₀=X_(min) being set to be the command operating point.
 24. Ashift control apparatus for the hybrid transmission as claimed in claim1, wherein the target value correcting section derives the realizableregion (A) on the two-dimensional coordinates with one axis calibratedwith a drive torque (To) and the other axis calibrated with the enginerevolution acceleration (d/dt)ωi which falls within a battery ratedpower, on the basis of the engine revolution acceleration (d/dt)ωi, anoutput revolution speed (ω₀) of the hybrid transmission, a runningresistance torque (T_(R)), an engine torque (T_(E)), and a batterycharge-and-discharge quantity (P_(B)), and derives another realizableregion (BC) of a drive torque a mechanically generable by themotor/generators (MG1, MG2) in addition to the realizable region (A), anoverlapped area of both of the realizable region (BC) constituting astill another realizable region (D).
 25. A shift control apparatus forthe hybrid transmission as claimed in claim 5, wherein the target valuecorrecting section derives the realizable region (A) expressed ontwo-dimensional coordinates of the drive torque (To) calculated in alateral axis thereof and of the input revolution calibrated in alongitudinal axis thereof, calculates two boundary lines prescribing therealizable region (A) on the basis of a battery rated power (P_(BMAX)),a running resistance torque (T_(R)), an engine torque (T_(R)), andspecifications of the hybrid transmission, derives points ofintersections between a straight line passing through the targetoperating point (x₀, y₀) which corresponds to a combination between thetarget drive torque x₀ (=T*_(oO)) and target input revolutionacceleration Y₀ (=u_(io)) and which is parallel to an input revolutionacceleration axis which is a longitudinal axis of the two-dimensionalcoordinates, with the drive axle as a lateral axis and the two boundarylines prescribing the realizable region and determines whether a pointof y₀ of the target operating point (x₀, y₀) falls in a space of thetwo-dimensional coordinates between longitudinal axis coordinates of thepoints of intersections (y₁ and y₂).
 26. A shift control apparatus forthe hybrid transmission as claimed in claim 25, wherein, whendetermining that the point of x₀ falls out of the space between y₁ andy₂, the target value correcting section determines that the targetoperating point is out of the realizable region (A) and derives a pointof intersection (x₀, y₀) between one of the realizable region boundarylines which is nearer to the target operating point (x₀, y₀) and a lineexpressing that To=x₀, the point of intersection (x₀, y₀) being a pointof y_(c) which is nearest to the point y₀ and is within the realizableregion and to which the target input revolution acceleration u_(io) ismoved, calculates the input revolution acceleration lower limit setvalue (y_(min)) on the basis of a deviation between the target inputrevolution speed and an actual input revolution speed and an actualinput revolution speed, and determines whether y_(c) is located towardy₀ side with respect to y_(min), the drive torque T*₀ and apost-correction input revolution acceleration command value (u_(i)). 27.A shift control apparatus for the hybrid transmission as claimed inclaim 26, wherein, when determining that y_(c) is not located toward y₀side with respect to y_(min), the target value correcting section sets apoint of intersection between one of the two boundary lines prescribingthe realizable region (A) which is nearer to the target operating point(x₀, y₀) and a line expressing the input revolution acceleration(d/dt)ωi=y_(min) to be a command operating point, the drive torque T*oand the input revolution acceleration (u_(i)) to be a post-correctiondrive torque command value (T*o) and a post-correction input revolutionacceleration command value (u_(i)).
 28. A shift control apparatus forthe hybrid transmission as claimed in claim 24, wherein the target valuecorrecting section determines whether a target driving torque (T*_(oO))and a target input revolution acceleration (u_(io)) are feasibledepending upon whether a plurality of predetermined conditions aresatisfied and wherein, when the target value correcting sectiondetermines that the target driving torque (T*_(oO)) and the target inputrevolution acceleration (u_(io)) are feasible when the predeterminedconditions are satisfied, a target operating point which is thecombination of the target driving torque x₀ (=T*_(oO)) and target inputrevolution acceleration y₀ (=u_(io)) is directly set to be apost-correction drive torque command value (T*o) and a post-correctiontarget input revolution acceleration (u_(i)) and, when the target valuecorrecting section determines that the target driving torque (T*_(oO))and the target input revolution acceleration (u_(io)) is not feasible, aline segment connecting an origin of the two-dimensional coordinates andtarget operating point (x₀, y₀) is intersected with one of boundarylines of region A, a region B, and a region C which is within therealizable region (D) and is a nearest point to the target operatingpoint is set to be the command operating point.
 29. A shift controlapparatus for the hybrid transmission as claimed in claim 24, whereinthe target value correcting section determines whether a target drivingtorque (T*_(oO)) and a target input revolution acceleration (u_(io)) arefeasible depending upon whether a plurality of predetermined conditionsare satisfied and wherein, when the target value correcting sectiondetermines that the target driving torque (T*_(oO)) and the target inputrevolution acceleration (u_(io)) are feasible when the predeterminedconditions are satisfied, a target operating point which is thecombination of the target driving torque x₀ (=T*_(oO)) and target inputrevolution acceleration y₀ (=u_(io)) is directly set as apost-correction drive torque command value (T*o) and a post-correctiontarget input revolution acceleration (u_(i)), and, when the target valuecorrecting section determines that the target driving torque (T*_(oO))and the target input revolution acceleration (u_(io)) are not feasiblewhen the predetermined conditions are not satisfied, the target valuecorrecting section derives a point of intersection (x₀, y_(c)) between aboundary line of regions A, B, and C and a line expressing To=x₀, thepoint of intersection (x₀, y_(c)) being a point of y_(c) within therealizable region D which is nearest to y₀ to which the target inputrevolution acceleration (u_(io)) is moved with the target drive torque(T*_(oO)) left unchanged, calculates the input revolution accelerationlower limit set value (y_(min)) on the basis of a deviation between thetarget input revolution speed (ω*i) and an actual input revolution speed(ωi), and determines whether a value of y_(c) is located toward a valueof y₀ side with respect to y_(min).
 30. A shift control apparatus forthe hybrid transmission as claimed in claim 29, wherein, when the valueof y_(c) is located toward the value of y₀ side with respect to y_(min),the target value correcting section sets the point of intersection (x₀,y_(c)) to the command operating point, the target drive torque (T*₀) andengine revolution acceleration (u_(i)) at the command operating pointbeing set to be a post correction drive torque (T*₀) and apost-correction engine revolution acceleration (u_(i)) at the commandoperating point.
 31. A shift control apparatus for the hybridtransmission as claimed in claim 30, wherein, when the value of y_(c) isnot located toward the value of y₀ side with respect to y_(min), thetarget value correcting section sets one of points of intersections ofboundary lines of regions A, B, and C and a line expressing the inputrevolution acceleration (d/dt)ωi=y_(min) which is nearest to the targetoperating point (x₀, y₀) within the realizable region (D) as a commandoperating point, the target drive torque (T*o) and the target inputrevolution acceleration (u_(i)) at the command operating point being setas a post-correction drive torque command value (T*_(o)) and apost-correction input revolution acceleration command value (u_(i)). 32.A shift control apparatus for the hybrid transmission as claimed inclaim 24, wherein the target value correcting section determines whethera target driving torque (T*_(oO)) and a target input revolutionacceleration (u_(io)) are feasible depending upon whether a plurality ofpredetermined conditions are satisfied and wherein, when the targetvalue correcting section determines that the target driving torque(T*_(oO)) and the target input revolution acceleration (u_(io)) arefeasible when the predetermined conditions are satisfied, a targetoperating point which is the combination of the target driving torque x₀(=T*_(oO)) and target input revolution acceleration y₀ (=u_(io)) isdirectly set as a post-correction drive torque command value (T*₀) and apost-correction target input revolution acceleration (u_(i)), and, whenthe target value correcting section determines that the target drivingtorque (T*_(oO)) and the target input revolution acceleration (u_(io))are not feasible when the predetermined conditions are not satisfied,the target value correcting section derives a point of intersection(x_(c), y₀) between each boundary line of regions A, B, and C and a lineexpressing (d/dt)ωi=y₀, the point of intersection (x_(c), y₀) being apoint of x_(c) within the realizable region D which is nearest to x₀ towhich the target drive torque (T*_(oO)) is moved with the target inputrevolution acceleration (i_(oO)) left unchanged, calculates the drivetorque predetermined lower limit set value (x_(min)) on the basis of adeviation between the target input revolution speed and an actual inputrevolution speed, and determines whether a value of x_(c) is locatedtoward a value of x₀ side with respect to x_(min).
 33. A shift controlapparatus for the hybrid transmission as claimed in claim 32, wherein,when x_(c) is located toward the value of x₀ side with respect tox_(min), the target value correcting section sets the point ofintersection (x_(c), y₀) to be a command operating point, the drivetorque (T*o) and the input revolution acceleration at the commandoperating point being set as a post-correction drive torque commandvalue (T*o) and a post-correction input acceleration command value(u_(i)) and, when x_(c) is not located toward the value of x₀ side withrespect to x_(min), the target value correcting section sets one of thepoints of intersections between the boundary lines of regions A, B, andC and a line expressing drive torque To=x_(min) which is nearest to thetarget operating point (x₀, y₀) within the realizable region (D) as thecommand operating point, the drive torque (T*o) and the input revolutionacceleration (u_(i)) at the command operating point being set to be apost-correction drive torque command value (T*o) and to be apost-correction input revolution acceleration (u_(i)).
 34. A shiftcontrol method for a hybrid transmission, the hybrid transmissioncomprising: a plurality of revolutional members which are enabled to bearranged on a predetermined lever diagram; and a differential unithaving two degrees of freedom such that if revolution states of tworevolutional members of the plurality of revolutional members aredetermined, the revolutional states of the other revolutional members ofthe plurality of revolutional members are determined, an input of a mainpower source, an output to a drive system, and a plurality ofmotor/generators (MG1, MG2) are coupled to the respective revolutionalmembers of the differential unit to adjust a power from themotor/generators in such a manner that a shift ratio between the mainpower source and the drive system is varied continuously, and the shiftcontrol method comprising: calculating a target drive torque (T*o) tothe drive system in accordance with a driving condition; calculating atarget input revolution speed (ω*_(E)) of one of the revolutionalmembers which is coupled to the main power source (ENG); calculating atarget input revolution acceleration (u_(io)) to converge an actualinput revolution (ωi) into the target input revolution speed (107 *i);and correcting at least one of the target drive torque (T*_(oO)) and thetarget input revolution acceleration (u_(io)) to be a value within arealizable region to be set as a drive torque command value (T*o) or aninput revolution acceleration command value (u_(io)) in such a mannerthat polarities of the target drive torque (T*o) and the target inputrevolution acceleration (u_(io)) are left unchanged, wherein in a casewhere a combination of the target drive torque (T*o) with the targetinput revolution acceleration (u_(io)) falls out of a realizable regionon two-dimensional coordinates of the drive torque (To) and the inputrevolution acceleration {(d/dt)ωi} related to a combination of the drivetorque and the input revolution acceleration which is feasible in astate of the present motor/generators, a battery (P_(B)) for themotor/generators (MG1, MG2), and the main power source, at thecorrecting of at least one of the target drive torque and the targetinput revolution acceleration, making the drive torque command value(T*o) and the input revolution acceleration command value (u_(i))contribute to controls of the main power source (ENG) and themotor/generators (MG1, MG2) in place of the target drive torque(T*_(oO)) and the target input revolution acceleration (u_(io)).